The Portsmouth Athenæum is an independent membership library, gallery, and museum in Portsmouth, New Hampshire, United States. It preserves and provides access to an extensive collection of manuscripts, rare books, photographs, artworks and artifacts, and digital collections related to local history and genealogy, in addition to a circulating library for its membership. As an intellectual center of the community, it sponsors exhibitions, concerts, lectures, and other educational and cultural programs. The building, dating to 1805, has been listed on the National Register of Historic Places since 1973.