A special library is a library that provides specialized information resources on a particular subject, serves a specialized and limited clientele, and delivers specialized services to that clientele. Special libraries include corporate libraries, government libraries, law libraries, medical libraries, museum libraries, news libraries, and nonprofit libraries. Special libraries also exist within academic institutions, including law school libraries and medical school libraries. These libraries are included as special libraries because they are often funded separately from the rest of the university and they serve a targeted group of users.
Special libraries often have a more specific clientele than libraries in traditional educational or public settings, and deal with more specialized kinds of information. They are developed to support the mission of their sponsoring organization and their collections and services are more targeted and specific to the needs of their clientele. Special libraries may or may not be open to the general public. Those that are open to the public may offer services similar to research, reference, public, academic, or children's libraries, often with restrictions such as only lending books to patients at a hospital or restricting the public from parts of a military collection. Many special libraries are not open to the general public, though access may be requested for specialized research by request. Special libraries are also sometimes known as information centers. Some authors differentiate special libraries from information centers by defining the latter as having "a very narrow scope." They are generally staffed by librarians, although many librarians employed in special libraries are specialists in the library's field rather than generally trained librarians, and often are not required to have advanced degrees in specifically library-related field due to the specialized content and clientele of the library. However, it is not uncommon for librarians at special libraries to have both a library science degree as well as a degree or experience of some type in the field their library specializes in as opposed to either only library science or field specific experience.
Special libraries are "special" in their collections, users, and services. For example, a research institute's library may supply information to scientists who lack the time to visit the library. Current Awareness Service (CAS) and Selective Dissemination of Information (SDI) are very common. The listing of special libraries in this article is not comprehensive. Special libraries as a field are defined by not being public, school, academic, or national libraries. Special libraries may be called libraries, information centers, information resource collections, or other names, typically decided by the institution that the library is attached to, and may or may not have a generally trained and qualified librarian on staff.