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 494 seats on two levels. It is a Grade II Listed Building.

The Duchess Theatre was purchased in 2005 by Nica Burns and Max Weitzenhoffer forming part of the Nimax Theatres group.

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.

The original interiors were Art Deco in style, designed by Marc Henri and Gaston Laverder. These were later redesigned by Mary Wyndham-Lewis. The only remaining features of the original decorations in the auditorium are two bas-reliefs by Maurice Lambert, flanking the proscenium arch.