Dr Williams's Library is a small research library located in Gordon Square in Bloomsbury, London.
It was founded using the estate of Dr Daniel Williams (1643–1716) as a theological library, intended for the use of ministers of religion, students and others studying theology, religion and ecclesiastical history. Several of its first directors were ministers associated with Newington Green Unitarian Church. The library opened in 1729 at Red Cross Street with its original benefaction of around 7600 books from Williams. Its site moved frequently, until the acquisition of its present home, University Hall in Gordon Square, in 1890. It has always had close ties with the Unitarians, and when a Doodlebug destroyed Essex Hall, the headquarters of the General Assembly of Unitarian and Free Christian Churches, the Library offered a few spare rooms to displaced workers. They stayed for 14 years, until 1958.
In addition to its theological holdings, the library contains collections of philosophy, history, literature, and related subjects. There is also a large collection of works on Byzantine history and culture bequeathed by Professor Norman H. Baynes (1877–1961). In 1976, it acquired the library of New College London.
The library is known to researchers of history and genealogy for its holdings of pre-19th century material relating to Protestant nonconformity in England, including papers by Dissenting minister Joshua Toulmin, D.D. It holds the manuscript of a 17th-century diary written by Roger Morrice (1628–1702), an English Puritan minister and political journalist. It covers the years 1677 to 1691, and in 2007 the Boydell Press published a six volume edition of Roger Morrice's Entring Book. The library also has many manuscripts of Philip Doddridge (1702 – 1751), a Nonconformist leader, educator, and hymnwriter, including letters between Doddridge and his wife, his wife's diary and some of his artifacts.