A library is a collection of information, sources, resources, and services, and the structure in which it is housed: it is organized for use and maintained by a public body, an institution, or a private individual. In the more traditional sense, a library is a collection of books. The term can mean the collection, the building that houses such a collection, or both.
The collection and services are used by people who choose not to — or cannot afford to — purchase an extensive collection themselves, who need material no individual can reasonably be expected to have, or who require professional assistance with their research.
However, with the collection of media other than books for storing information, many libraries are now also repositories and access points for maps, prints, or other documents and works of art on various storage media such as microform (microfilm/microfiche), audio tapes, CDs, LPs, cassettes, videotapes, and DVDs. Libraries may also provide public facilities to access CD-ROMs, subscription databases, and the Internet.
Thus, modern libraries are increasingly being redefined as places to get unrestricted access to information in many formats and from many sources. In addition to providing materials, they also provide the services of specialists, librarians, who are experts at finding and organizing information and at interpreting information needs.
More recently, libraries are understood as extending beyond the physical walls of a building, by including material accessible by electronic means, and by providing the assistance of librarians in navigating and analyzing tremendous amounts of knowledge with a variety of digital tools.
The term "library" has itself acquired a secondary meaning: "a collection of useful material for common use," and in this sense is used in fields such as computer science, mathematics and statistics, electronics and biology.
The first libraries were composed, for the most part, of unpublished records, a particular type of library called archives. Archaeological findings from the ancient city-states of Sumer have revealed temple rooms full of clay tablets in cuneiform script. These archives were made up almost completely of the records of commercial transactions or inventories, with only a few documents touching theological matters, historical records or legends. Things were much the same in the government and temple records on papyrus of Ancient Egypt.
The earliest discovered private archives were kept at Ugarit; besides correspondence and inventories, texts of myths may have been standardized practice-texts for teaching new scribes. There is also evidence of libraries at Nippur of about 1900 B.C. and those at Nineveh of about 700 B.C. as showing a library classification system.
 Libraries in the Hellenic world and Rome
Private or personal libraries made up of non-fiction and fiction books (as opposed to the state or institutional records kept in archives) first appeared in classical Greece, in the 5th century BC. The celebrated book collectors of Hellenistic Antiquity were listed in the late second century in Deipnosophistae:
Polycrates of Samos and Pisistratus who was tyrant of Athens, and Euclides who was himself also an Athenian and Nicorrates of Samos and even the kings of Pergamos, and Euripides the poet and Aristotle the philosopher, and Nelius his librarian; from whom they say our countryman Ptolemæus, surnamed Philadelphus, bought them all, and transported them, with all those which he had collected at Athens and at Rhodes to his own beautiful Alexandria.
All these libraries were Greek; the cultivated Hellenized diners in Deipnosophistae pass over the libraries of Rome in silence. By the time of Augustus there were public libraries near the forums of Rome: there were libraries in the Porticus Octaviae near the Theatre of Marcellus, in the temple of Apollo Palatinus, and in the Biblioteca Ulpiana in the Forum of Trajan. The state archives were kept in a structure on the slope between the Roman Forum and the Capitoline Hill.
Private libraries appeared during the late republic: Seneca inveighed against libraries fitted out for show by non-reading owners who scarcely read their titles in the course of a lifetime, but displayed the scrolls in bookcases (armaria) of citrus wood inlaid with ivory that ran right to the ceiling: "by now, like bathrooms and hot water, a library is got up as standard equipment for a fine house (domus). Libraries were amenities suited to a villa, such as Cicero's at Tusculum, Maecenas's several villas, or Livy the Younger's, all described in surving letters. At the Villa of the Papyri at Herculaneum, apparently the villa of Caesar's father-in-law, the Greek library has been partly preserved in volcanic ash; archaeologists speculate that a Latin library, kept separate from the Greek one, may await discovery at the site.
In the West, the first public libraries were established under the Roman Empire as each succeeding emperor strove to open one or many which outshone that of his predecessor. Unlike the Greek libraries, readers had direct access to the scrolls, which were kept on shelves built into the walls of a large room. Reading or copying was normally done in the room itself. The surviving records give only a few instances of lending features. As a rule Roman public libraries were bilingual: they had a Latin room and a Greek room. Most of the large Roman baths were also cultural centers, built from the start with a library, with the usual two room arrangement for Greek and Latin texts.
Libraries were filled with parchment scrolls as at Pergamum and on papyrus scrolls as at Alexandria: export of prepared writing materials was a staple of commerce. There were a few institutional or royal libraries like the Library of Alexandria which were open to an educated public, but on the whole collections were private. In those rare cases where it was possible for a scholar to consult library books there seems to have been no direct access to the stacks. In all recorded cases the books were kept in a relatively small room where the staff went to get them for the readers, who had to consult them in an adjoining hall or covered walkway.
In the sixth century, at the very close of the Classical period, the great libraries of the Mediterranean world remained those of Constantinople and Alexandria. Cassiodorus, minister to Theodoric, established a monastery at Vivarium in the heel of Italy with a library where he attempted to bring Greek learning to Latin readers and preserve texts both sacred and secular for future generations. As its unofficial librarian, Cassiodorus not only collected as many manuscripts as he could, he also wrote treatises aimed at instructing his monks in the proper uses of reading and methods for copying texts accurately. In the end, however, the library at Vivarium was dispersed and lost within a century.
With education firmly in Christian hands, however, many of the works of classical antiquity were no longer considered useful. Old texts were washed off the valuable parchment and papyrus, which were reused, forming palimpsests. As scrolls gave way to the new book-form, the codex, which was universally used for Christian literature, old manuscript scrolls were cut apart and used to stiffen leather bindings.
 Ancient Chinese libraries
Little is known about early Chinese libraries, save what is written about the imperial library which began with the Qin Dynasty. One of the curators of the imperial library in the Han Dynasty is believed to have been the first to establish a library classification system and the first book notation system. At this time the library catalog was written on scrolls of fine silk and stored in silk bags.
 Early Middle Ages
With the retrenchment of literacy in the Roman west during the fourth and fifth centuries, fewer private libraries were maintained, and those in unfortified villas proved to be among their most combustible contents.
 Middle Ages
Elsewhere in the Early Middle Ages, after the fall of the Western Roman Empire and before the rise of the large Western Christian monastery libraries beginning at Montecassino, libraries were found in scattered places in the Christian Middle East.
 Islamic libraries
In Persia many libraries were established by the Zoroastrian elite and the Persian Kings. Among the first ones was a royal library in Isfahan. One of the most important public libraries established around 667 AD in south-western Iran was the Library of Gundishapur. It was a part of a bigger scientific complex located at the Academy of Gundishapur. Upon the rise of Islam, libraries in newly Islamic lands knew a brief period of expansion in the Middle East, North Africa, Sicily and Spain. Like the Christian libraries, they mostly contained books which were made of paper, and took a codex or modern form instead of scrolls; they could be found in mosques, private homes, and universities. In Aleppo, for example the largest and probably the oldest mosque library, the Sufiya, located at the city's Grand Umayyad Mosque, contained a large book collection of which 10 000 volumes were reportedly bequeathed by the city's most famous ruler, Prince Sayf al-Dawla.  Some mosques sponsored public libraries. Ibn al-Nadim's bibliography Fihrist demonstrates the devotion of medieval Muslim scholars to books and reliable sources; it contains a description of thousands of books circulating in the Islamic world circa 1000, including an entire section for books about the doctrines of other religions. Unfortunately, modern Islamic libraries for the most part do not hold these antique books; many were lost, destroyed by Mongols, or removed to European libraries and museums during the colonial period.
By the 8th century first Iranians and then Arabs had imported the craft of papermaking from China, with a paper mill already at work in Baghdad in 794. By the 9th century completely public libraries started to appear in many Islamic cities. They were called "halls of Science" or dar al-'ilm. They were each endowed by Islamic sects with the purpose of representing their tenets as well as promoting the dissemination of secular knowledge. The 9th century Abbasid Caliph al-Mutawakkil of Iraq, even ordered the construction of a ‘zawiyat qurra literally an enclosure for readers which was `lavishly furnished and equipped.' In Shiraz Adhud al-Daula (d. 983) set up a library, described by the medieval historian, al-Muqaddasi, as`a complex of buildings surrounded by gardens with lakes and waterways. The buildings were topped with domes, and comprised an upper and a lower story with a total, according to the chief official, of 360 rooms.... In each department, catalogues were placed on a shelf... the rooms were furnished with carpets...'.  The libraries often employed translators and copyists in large numbers, in order to render into Arabic the bulk of the available Persian, Greek, Roman and Sanskrit non-fiction and the classics of literature. This flowering of Islamic learning ceased centuries later when learning began declining in the Islamic world, after many of these libraries were destroyed by Mongol invasions. Others were victim of wars and religious strife in the Islamic world. However, a few examples of these medieval libraries, such as the libraries of Chinguetti in West Africa, remain intact and relatively unchanged even today. Another ancient library from this period which is still operational and expanding is the Central Library of Astan Quds Razavi in the Iranian city of Mashhad, which has been operating for more than six centuries.
A number of distinct features of the modern library were introduced in the Islamic world, where libraries not only served as a collection of manuscripts as was the case in ancient libraries, but also as a public library and lending library, a centre for the instruction and spread of sciences and ideas, a place for meetings and discussions, and sometimes as a lodging for scholars or boarding school for pupils. The concept of the library catalogue was also introduced in medieval Islamic libraries, where books were organized into specific genres and categories.
The contents of these Islamic libraries were copied by Christian monks in Muslim/Christian border areas, particularly Spain and Sicily. From there they eventually made their way into other parts of Christian Europe. These copies joined works that had been preserved directly by Christian monks from Greek and Roman originals, as well as copies Western Christian monks made of Byzantine works. The resulting conglomerate libraries are the basis of every modern library today.
 Medieval Christian libraries
Medieval library design reflected the fact that these manuscripts--created via the labor-intensive process of hand copying--were valuable possessions. Library architecture developed in response to the need for security. Librarians often chained books to lecterns, armaria (wooden chests), or shelves, in well-lit rooms. Despite this protectiveness, many libraries were willing to lend their books if provided with security deposits (usually money or a book of equal value). Monastic libraries lent and borrowed books from each other frequently and lending policy was often theologically grounded. For example, the Franciscan monasteries loaned books to each other without a security deposit since according to their vow of poverty only the entire order could own property. In 1212 the council of Paris condemned those monasteries that still forbade loaning books, reminding them that lending is "one of the chief works of mercy." 
The early libraries located in monastic cloisters and associated with scriptoria were collections of lecterns with books chained to them. Shelves built above and between back-to-back lecterns were the beginning of bookpresses. The chain was attached at the fore-edge of a book rather than to its spine. Book presses came to be arranged in carrels (perpendicular to the walls and therefore to the windows) in order to maximize lighting, with low bookcases in front of the windows. This stall system (fixed bookcases perpendicular to exterior walls pierced by closely spaced windows) was characteristic of English institutional libraries. In Continental libraries, bookcases were arranged parallel to and against the walls. This wall system was first introduced on a large scale in Spain's El Escorial.
 Early modern libraries
From the fifteenth century in central and northern Italy, the assiduously assembled libraries of humanists and their enlightened patrons provided a nucleus around which an "academy" of scholars congregated in each Italian city of consequence. In Rome, the papal collections were brought together by Pope Nicholas V, in separate Greek and Latin libraries, and housed by Pope Sixtus IV, who consigned the Bibliotheca Apostolica Vaticana to the care of his librarian, the humanist Bartolomeo Platina in February 1475. In the sixteenth century Sixtus V bisected Bramante's Cortile del Belvedere with a cross-wing to house the Apostolic Library in suitable magnificence. The sixteenth and seventeenth centuries saw other privately-endowed libraries assembled in Rome: the Vallicelliana, formed from the books of Saint Filippo Neri, with other distinguished libraries such as that of Cesare Baronio, the Biblioteca Angelica founded by the Augustinian Angelo Rocca, which was the only truly public library in Counter-Reformation Rome; the Biblioteca Alessandrina with which Pope Alexander VII endowed the University of Rome; the Biblioteca Casanatense of the Cardinal Girolamo Casanate; and finally the Biblioteca Corsiniana founded by the bibliophile Clement XII Corsini and his nephew Cardinal Neri Corsini, still housed in Palazzo Corsini in via della Lungara.
A number of factors combined to create a "golden age of libraries" between 1600 and 1700: The quantity of books had gone up, as the cost had gone down, there was a renewal in the interest of classical literature and culture, nationalism was encouraging nations to build great libraries, universities were playing a more prominent role in education, and renaissance thinkers and writers were producing great works. Some of the more important libraries include the Bodleian Library at Oxford, the Library of the British Museum, the Mazarine Library in Paris, and the National Central Library in Italy, the Prussian State Library, the German State Library, the M.E. Saltykov-Schedrin State Public Library of St. Petersburg, and many more.
 Public libraries
The earliest example in England of a library to be endowed for the benefit of users who were not members of an institution such as a cathedral or college was the Francis Trigge Chained Library in Grantham, Lincolnshire, established in 1598. The library still exists and can justifiably claim to be the forerunner of later public library systems.The beginning of the modern, free, open access libraries really got its start in the U.K. in 1847. Parliament appointed a committee, led by, William Ewart, on Public Libraries to consider the necessity of establishing libraries through the nation: In 1849 their report noted the poor condition of library service, it recommended the establishment of free public libraries all over the country, and it led to the Public Libraries Act in 1850, which allowed all cities with populations exceeding 10,000 to levy taxes for the support of public libraries. Another important act was the 1870 Public School Law, which increased literacy, thereby the demand for libraries, so by 1877, more than 75 cities had established free libraries, and by 1900 the number had reached 300.  This finally marks the start of the public library as we know it. And these acts led to similar laws in other countries, most notably the U.S.
1876 is a well known year in the history of librarianship. The American Library Association was formed, as well as The American Library Journal, Melvil Dewey published his decimal based system of classification, and the United States Bureau of Education published its report, "Public libraries in the United States of America; their history, condition, and management." The American Library Association continues to play a major role in libraries to this day, and Dewey's classification system, although under heavy criticism of late, still remains as the prevailing method of classification used in the United States.
As the number of books in libraries increased, so did the need for compact storage and access with adequate lighting, giving birth to the stack system, which involved keeping a library's collection of books in a space separate from the reading room, an arrangement which arose in the 19th century. Book stacks quickly evolved into a fairly standard form in which the cast iron and steel frameworks supporting the bookshelves also supported the floors, which often were built of translucent blocks to permit the passage of light (but were not transparent, for reasons of modesty). With the introduction of electrical lighting, it had a huge impact on how the library operated. Also, the use of glass floors was largely discontinued, though floors were still often composed of metal grating to allow air to circulate in multi-story stacks. Ultimately, even more space was needed, and a method of moving shelves on tracks (compact shelving) was introduced to cut down on otherwise wasted aisle space.
Library 2.0, a term coined in 2005, is the library's response to the challenge of Google, and an attempt to meet the changing needs and wants of the users, using web 2.0 technology. Some of the aspects of Library 2.0 include, commenting, tagging, bookmarking, discussions, using social software, plug-ins, and widgets.  Inspired by web 2.0, it is an attempt to make the library a more user driven institution.
 Types of libraries
Libraries can be divided into categories by several methods:
- by the entity (institution, municipality, or corporate body) that supports or perpetuates them
- by the type of documents or materials they hold
- by the subject matter of documents they hold
- by the users they serve
- military communities
- users who are blind or visually/physically handicapped (see National Library Service for the Blind and Physically Handicapped)
- by traditional professional divisions
- Academic libraries — These libraries are located on the campuses of colleges and universities and serve primarily the students and faculty of that and other academic institutions. Some academic libraries, especially those at public institutions, are accessible to members of the general public in whole or in part.
- Public libraries or public lending libraries — These libraries provide service to the general public and make at least some of their books available for borrowing, so that readers may use them at home over a period of days or weeks. Typically, libraries issue library cards to community members wishing to borrow books. Many public libraries also serve as community organizations that provide free services and events to the public, such as reading groups and toddler story time.
- Research libraries — These libraries are intended for supporting scholarly research, and therefore maintain permanent collections and attempt to provide access to all necessary material. Research libraries are most often academic libraries or national libraries, but many large special libraries have research libraries within their special field and a very few of the largest public libraries also serve as research libraries.
- School libraries — Most public and private primary and secondary schools have libraries designed to support the school's curriculum.
- Special libraries — All other libraries fall into this category. Many private businesses and public organizations, including hospitals, museums, research laboratories, law firms, and many government departments and agencies, maintain their own libraries for the use of their employees in doing specialized research related to their work. Special libraries may or may not be accessible to some identified part of the general public. Branches of a large academic or research libraries dealing with particular subjects are also usually called "special libraries": they are generally associated with one or more academic departments. Special libraries are distinguished from special collections, which are branches or parts of a library intended for rare books, manuscripts, and similar material. 
- The final method of dividing library types is also the simplest.
Many institutions make a distinction between circulating libraries (where materials are expected and intended to be loaned to patrons, institutions, or other libraries) and collecting libraries (where the materials are selected on a basis of their natures or subject matter). Many modern libraries are a mixture of both, as they contain a general collection for circulation, and a reference collection which is often more specialized, as well as restricted to the library premises.
Also, the governments of most major countries support national libraries. Three noteworthy examples are the U.S. Library of Congress, Canada's Library and Archives Canada, and the British Library. A typically broad sample of libraries in one state in the U.S. can be explored at Every Library In Illinois.
Libraries have materials arranged in a specified order according to a library classification system, so that items may be located quickly and collections may be browsed efficiently. Some libraries have additional galleries beyond the public ones, where reference materials are stored. These reference stacks may be open to selected members of the public. Others require patrons to submit a "stack request," which is a request for an assistant to retrieve the material from the closed stacks.
Larger libraries are often broken down into departments staffed by both paraprofessionals and professional librarians.
- Circulation handles user accounts and the loaning/returning and shelving of materials.
- Collection Development orders materials and maintains materials budgets.
- Reference staffs a reference desk answering user questions (using structured reference interviews), instructing users, and developing library programming. Reference may be further broken down by user groups or materials; common collections are children's literature, young adult literature, and genealogy materials.
- Technical Services works behind the scenes cataloguing and processing new materials and deaccessioning weeded materials.
 Library use
Patrons may not know how to fully use the library's resources. This can be due to some individuals' unease in approaching a staff member. The greatest impact, though are the ways in which a library's content is displayed or accessed. An antiquated or clumsy search system, or a staff unwilling or untrained to engage its patrons will limit a library's usefulness. In United States public libraries, beginning in the 19th century these problems drove the emergence of the library instruction movement, which advocated library user education. One of the early leaders was John Cotton Dana. The basic form of library instruction is generally known as information literacy.
Libraries inform their users of what materials are available in their collections and how to access that information. Before the computer age, this was accomplished by the card catalog — a cabinet containing many drawers filled with index cards that identified books and other materials. In a large library, the card catalog often filled a large room. The emergence of the Internet, however, has led to the adoption of electronic catalog databases (often referred to as "webcats" or as OPACs, for "online public access catalog"), which allow users to search the library's holdings from any location with Internet access. This style of catalog maintenance is compatible with new types of libraries, such as digital libraries and distributed libraries, as well as older libraries that have been retrofitted. Electronic catalog databases are disfavored by some who believe that the old card catalog system was both easier to navigate and allowed retention of information, by writing directly on the cards, that is lost in the electronic systems. This argument is analogous to the debate over paper books and e-books. While they have been accused of precipitously throwing out valuable information in card catalogs, most modern libraries have nonetheless made the movement to electronic catalog databases. Large libraries may be scattered within multiple buildings across a town, each having multiple floors, with multiple rooms housing the resources across a series of shelves. Once a user has located a resource within the catalog, they must then utilise navigational guidance to retrieve the resource physically; a process that may be assisted through signage, maps, GPS systems or RFID tagging.
Finland has the highest number of registered book borrowers per capita in the world. Over half of Finland's population are registered borrowers. In the U.S., public library users have borrowed roughly 15 books per user per year from 1856 to 1978. From 1978 to 2004, book circulation per user declined approximately 50%. The growth of audiovisuals circulation, estimated at 25% of total circulation in 2004, accounts for about half of this decline.
 Library management
Basic tasks in library management include the planning of acquisitions (which materials the library should acquire, by purchase or otherwise), library classification of acquired materials, preservation of materials (especially rare and fragile archival materials such as manuscripts), the deaccessioning of materials, patron borrowing of materials, and developing and administering library computer systems. More long-term issues include the planning of the construction of new libraries or extensions to existing ones, and the development and implementation of outreach services and reading-enhancement services (such as adult literacy and children's programming).
See public library for funding issues for public libraries.
 Famous libraries
- See also: Great libraries of the ancient world
Some of the greatest libraries in the world are research libraries. The most famous ones include The Humanities and Social Sciences Library of the New York Public Library in New York City, the Russian National Library in St Petersburg, the British Library in London, Bibliothèque nationale de France in Paris, National Library of Spain in Madrid, and the Library of Congress in Washington, D.C..
- Ambrosian Library in Milan opened to the public, December 8, 1609.
- Baghdad's House of Wisdom, founded in 8th century AD.
- Bibliothèque Nationale de France (BNF) in Paris, 1720.
- Bodleian Library at University of Oxford 1602, books collection begin around 1252.
- Boston Public Library in Boston, 1826.
- British Library in London created in 1973 by the British Library Act of 1972 (Originally part of the British Museum founded 1753).
- British Library of Political and Economic Science in London, 1896.
- Butler Library at Columbia University, 1934
- Cambridge University Library at University of Cambridge, 1931.
- Carnegie Library of Pittsburgh in Pittsburgh, 1895.
- Carnegie library Total of 2,509, between 1883 and 1929.
- Carolina Rediviva at Uppsala University, 1841.
- Dutch Royal Library in The Hague, 1798.
- Egypt's Library of Alexandria (founded in 3rd century BC) and modern Bibliotheca Alexandrina.
- Egypt's library of Cairo, founded in 10th century.
- Firestone Library at Princeton University, 1948
- Fisher Library at the University of Sydney (largest in the Southern Hemisphere), 1908
- Franklin Public Library in Franklin, Massachusetts (the first public library in the U.S.; original books donated by Benjamin Franklin in 1731)
- Free Library of Philadelphia in Philadelphia established February 18, 1891.
- Garrison Library in Gibraltar, 1793.
- Harold B. Lee Library at Brigham Young University, 1924.
- Haskell Free Library and Opera House, which straddles the Canada-US border.
- House of Commons Library, Westminster, London. Established 1818.
- Islamic Spain's library of Cordoba, founded in 9th century.
- Library of Ashurbanipal at Nineveh, founded between 669-631 BC.
- The European Library, 2004
- Tripoli's Dar il-'ilm, destroyed in 1109.
- ITU Mustafa Inan Library. Established 1795. The largest collection on technical (science and engineering) materials in Turkey.
- Jagiellonian Library at Jagiellonian University in Krakow, Poland, 1364.
- Jenkins Law Library in Philadelphia founded 1802.
- John Rylands Library in Manchester 1972.
- Leiden University Library at Leiden University in Leiden began at 1575 with confiscated monastery books. Officially open in October 31, 1587.
- Library of Congress in Washington, D.C. 1800.
- Library of Sir Thomas Browne, 1711
- Mitchell Library in Glasgow (Europe's largest public reference library)
- Multnomah County Library in Oregon, largest public library west of the Mississippi River, 1864.
- National Library of Australia in Canberra, Australia
- National Library of Belarus in Minsk, 1922.
- National Library of Iran, 1937.
- National Library of Ireland in Dublin, 1877.
- National library of Israel (formerly: Jewish National and University Library) in Jerusalem, Israel, 1892.
- National Library of Scotland in Edinburgh, 1925.
- National Library of Spain in Madrid, 1711.
- National Library of Wales in Aberystwyth, 1907.
- New York Public Library in New York
- Osler Library of the History of Medicine, McGill University, Montreal, Canada
- Powell Library at UCLA, part of the UCLA Library.
- Regenstein Library at the University of Chicago, one of the largest repositories of books in the world.
- Royal Library in Copenhagen, 1793.
- Russian State Library in Moscow, 1862.
- Sassanid's ancient Library of Gondishapur around 489.
- Seattle Central Library
- Staatsbibliothek in Berlin
- State Library of New South Wales in Sydney
- State Library of Victoria in Melbourne
- Sterling Memorial Library at Yale University, 1931.
- St. Marys Church, Reigate, Surrey houses the first public lending library in England. Opened 14 March 1701.
- The St. Phillips Church Parsonage Provincial Library, established in 1698 in Charleston, South Carolina, was the first public lending library in the American Colonies. See also Benjamin Franklin's free public library in Philadelphia, Pennsylvania.
- Trinity College Library, in Trinity College, Dublin, the largest library in Ireland. Since 1592.
- Vatican Library in Vatican City, 1448 (but existed before).
- Wellcome Library in London
- Widener Library at Harvard University (Harvard University Library including all branches has the largest academic collection overall.)
Some libraries devoted to a single subject:
- Chess libraries
- Esperanto libraries
- Family History Library in Salt Lake City, Utah, the world's largest genealogy library.
For more extensive lists, see
List of libraries
Libraries here should have a corresponding article in Wikipedia, or at least state the reason they are notable.
- Advocates' Library, Edinburgh, Scotland
- Archive for Research in Archetypal Symbolism
- Astan Quds Razavi's Central Library, Mashhad, Iran
- Baltimore County Public Library, Baltimore, Maryland
- Bayerische Staatsbibliothek, Munich, Bavaria, Germany
- Beinecke Rare Book and Manuscript Library, New Haven, Connecticut
- Biblioteca Nacional de España, Madrid
- Biblioteca Nacional de Portugal, Lisbon
- Bibliotheca Alexandrina, Egypt
- Bibliothèque nationale de France, Paris
- Birmingham Central Library, England
- Bizzell Memorial Library, University of Oklahoma, Norman, Oklahoma
- Bodleian Library, Oxford
- Boston Public Library, U.S.
- Botanical Research Institute of Texas Library, Fort Worth, Texas
- British Library, London
- Brooklyn Public Library, U.S.
- Burton Barr Central Library, Phoenix, Arizona
- Cambridge University Library
- Carolina Rediviva at Uppsala University
- Catholic National Library, Farnborough, Hampshire
- Center for Jewish History, Manhattan
- Cerritos Millennium Library in Cerritos, California
- Charles V. Park Library at Central Michigan University, Mount Pleasant, Michigan
- Chekhov Library in Taganrog
- Chetham's Library in Manchester
- Chicago Public Library, Chicago, Illinois, U.S.
- Cincinnati Public Library, Cincinnati, Ohio
- City of Playford Library Service in Adelaide, Australia
- CISTI, Ottawa
- Clinton-Macomb Public Library, Clinton Township, Michigan
- College of DuPage Library, Glen Ellyn, Illinois
- Columbia Public Library, Columbia, Missouri
- Columbus Metropolitan Library, Columbus, Ohio
- Contra Costa County Library, Pleasant Hill, California
- Cornish Studies Centre, Redruth, Cornwall, UK
- Cuyahoga County Public Library, Cleveland, Ohio
- Danish Royal Library in Copenhagen, Denmark
- Deutsche Bücherei Leipzig, Leipzig
- Dr Williams's Library, Bloomsbury, London
- Duchess Anna Amalia Library, Weimar, Germany
- Enoch Pratt Free Library, Baltimore, Maryland
- Family History Library, Salt Lake City, Utah
- Folger Shakespeare Library, Washington, DC
- Francis Skaryna Belarusian Library and Museum, London, United Kingdom
- Frank Melville Jr. Memorial Library, State University of New York at Stony Brook, Stony Brook, New York
- Free Library of Philadelphia, Philadelphia
- Glasgow University Library, Scotland
- Grande Bibliothèque du Québec, Montreal
- Haskell Free Library and Opera House
- Hilandar Research Library, Ohio State University
- Hong Kong Central Library, Causeway Bay, Hong Kong Island
- Houston Public Library, Texas
- Huntington Library, San Marino, California
- Jenkins Law Library, Philadelphia
- John Rylands Library
- Kedermister Library
- Koninklijke Bibliotheek, Netherlands
- Leiden University Library, Leiden, Netherlands
- Library of Alexandria, ancient Egypt
- Library of Congress, Washington, D.C.
- Library of Parliament, Ottawa
- Library of Sir Thomas Browne
- Library of the Russian Academy of Sciences
- Lied Library, University of Nevada, Las Vegas
- London Library
- Los Angeles Central Library
- Louisville Free Public Library, Louisville, Kentucky
- Louisville Public Library, Louisville, Ohio, USA
- Luís Ángel Arango Library, Bogotá, Colombia
- Malek National Library, Tehran, Iran
- Marathon County Public Library (MCPL), Wausau, Wisconsin
- Marsh's Library in Dublin
- Mark O. Hatfield Library, at Willamette University
- Michigan State University Libraries
- Milli Kütüphane (National Library of Turkey, Ankara)
- Minneapolis Public Library, Minneapolis, Minnesota
- Mitchell Library, Glasgow
- Moorland-Spingarn Research Center
- Multnomah County Library, Multnomah County, Oregon
- National Agricultural Library
- National Diet Library, Tokyo and Kyoto, Japan
- National Library of Australia, Canberra
- National Library of Canada
- National Library of India, Kolkata
- National Library of Iran, Tehran
- National Library of Ireland, Dublin
- National Library of New Zealand, Wellington
- National Library of Medicine
- National Library of Pakistan, Islamabad, Pakistan
- National Library of Scotland, Edinburgh
- National Library of Serbia, Belgrade
- National Library of Wales, Aberystwyth
- National Library, Singapore
- New Orleans Public Library
- New York Public Library, New York, New York
- Newberry Library, Chicago, Illinois
- Openbare Bibliotheek Amsterdam, Netherlands
- Oregon State Library, Salem, Oregon
- Park Ridge Public Library, Park Ridge, Illinois
- Peckham Library
- Pepys Library, Magdalene College, Cambridge
- Pikes Peak Library District,Colorado Springs, Colorado
- Plainfield Public Library District, Plainfield, Illinois
- Regenstein Library, University of Chicago, Chicago, Illinois
- Robarts Library, University of Toronto, Canada
- Royal Library of Sweden
- Ruskin Library at Lancaster University, UK
- Russian National Library in St Petersburg
- Russian State Library in Moscow
- Salt Lake City Public Library
- San Antonio Public Library
- Schlesinger Library
- Seattle Central Library
- South San Francisco Public Library
- Southfield Public Library, Southfield, Michigan
- SS. Cyril and Methodius National Library, Sofia, Bulgaria
- State Library of Victoria, Melbourne
- Texas A&M University Libraries, College Station, Texas
- Topeka & Shawnee County Public Library, Topeka, Kansas
- Toronto Public Library, Toronto
- Toronto Reference Library, Toronto
- Twinsburg Public Library
- UC Berkeley Library
- UCLA Library
- University of Sydney Library, Sydney
- Valley Library, Oregon State University
- Vancouver Public Library, Vancouver
- Vatican Library in Vatican City
- W.E.B. Du Bois Library, University of Massachusetts Amherst
- Wellcome Library, London
- Williams Research Center, New Orleans, Louisiana
- University of Coimbra General Library, Coimbra, Portugal
- Winnipeg Public Library
- Wren Library, Trinity College, Cambridge
- Yale University Library, Yale University
- Yiu Tung Public Library, Shau Kei Wan, Hong Kong Island, Hong Kong