St Martin's Theatre is a West End theatre, located in West Street, near Charing Cross Road, in the London Borough of Camden. It was designed by W.G.R. Sprague as one of a pair of theatres, with the Ambassadors Theatre. The 19th Baron Willoughby de Broke, together with B.A. (Bertie) Meyer, commissioned Sprague to design the St Martin's. Although the Ambassadors opened in 1913, the St Martin's construction was delayed by the outbreak of World War I. The theatre is still owned by the Willoughby de Broke family.
The first production at the theatre was the spectacular Edwardian musical comedy Houp La!, starring Gertie Millar, which opened on 23 November 1916. The producer was the impresario Charles B. Cochran, who took a 21 year lease on the new theatre.
Many famous British actors have passed through St Martin's. In April 1923 Basil Rathbone played Harry Domain in R.U.R. and in June 1927 Henry Daniell appeared there as Gregory Brown in Meet the Wife. Successes at the theatre included Hugh Williams's play (later a film) The Grass is Greener, John Mortimer's The Wrong Side of the Park and the thriller Sleuth (1970).
After Cochran, Bertie Meyer ran the theatre intermittently until 1967, when his son R.A.(Ricky) Meyer became administrator for the next two decades.
Agatha Christie's "The Mousetrap" transferred in March 1974 where it still remains, holding the record for the longest running show in the world.
The theatre was Grade II listed by English Heritage in March 1973.
This theatre is one of the 40 theatres featured in the 2012 DVD documentary series Great West End Theatres, presented by Donald Sinden.