Library science (or Library and Information science) is an interdisciplinary field that applies the practices, perspectives, and tools of management, information technology, education, and other areas to libraries; the collection, organization, preservation, and dissemination of information resources; and the political economy of information. The first school for library science was founded by Melvil Dewey at Columbia University in 1887.

Historically, library science has also included archival science. This includes how information resources are organized to serve the needs of select user groups, how people interact with classification systems and technology, how information is acquired, evaluated and applied by people in and outside of libraries as well as cross-culturally, how people are trained and educated for careers in libraries, the ethics that guide library service and organization, the legal status of libraries and information resources, and the applied science of computer technology used in documentation and records management.

Academic courses in library science typically include collection management, information systems and technology, research methods, cataloging and classification, preservation, reference, statistics and management. Library science is constantly evolving, incorporating new topics like database management, information architecture and knowledge management, among others.

There is no generally agreed distinction between the terms library science, librarianship, library and information science and information science, and to a certain extent they are interchangeable, perhaps differing most significantly in connotation. The term library and information science (LIS) is often used; most librarians consider it as only a terminological variation, intended to emphasize the scientific and technical foundations of the subject and its relationship with information science. LIS should not be confused with information theory, the mathematical study of the concept of information. LIS can also be seen as an integration of the two fields library science and information science, which were separate at one point.