The Library of Congress Classification (LCC) is a system of library classification developed by the Library of Congress in the United States, which can be used for shelving books in a library. LCC is mainly used by large research and academic libraries, while most public libraries and small academic libraries used the Dewey Decimal Classification system. The classification was developed by James Hanson, with assistance from Charles Martel, in 1897, while they were working at the Library of Congress. It was designed specifically for the purposes and collection of the Library of Congress to replace the fixed location system developed by Thomas Jefferson.

A library classification is a system used within a library to organize materials, including books, sound and video recordings, electronic materials, etc., both on shelves and in catalogs and indexes. Each item is typically assigned a call number, which identifies the location of the item within the system. Materials can be arrange by many different factors, typically in either a hierarchical tree structure based on the subject or using a faceted classification system, which allows the assignment of multiple classifications to an object, enabling the classifications to be ordered in many ways.