The Duchess Theatre is a West End theatre in the City of Westminster, London, located in Catherine Street near Aldwych. The theatre opened on 25 November 1929 and is one of the smallest West End theatres with a proscenium arch. It has 479 seats on two levels.
The Duchess Theatre was designed by Ewen Barr and constructed by F. G. Minter Ltd for Arthur Gibbons. The theatre is built with the stalls below street level, both to overcome the scale of the site and to maintain the rights of neighbours to ancient lights. The theatre opened on 25 November 1929 with a play called Tunnel Trench by Hubert Griffith. The interior decoration scheme was introduced in 1934 under the supervision of Mary Wyndham Lewis, wife of J. B. Priestley.