The Deep Blue Sea is a British stage play by Terence Rattigan from 1952. Rattigan based his story and characters in part on his secret relationship with Kenny Morgan, and the aftermath of the end of their relationship. The play was first performed in London on 6 March 1952, directed by Frith Banbury, and won praise for actress Peggy Ashcroft, who co-starred with Kenneth More. In the US, the Plymouth Theater staged the play in October 1952, with Margaret Sullavan. The play with Sullavan subsequently transferred to Broadway, with its Broadway premiere on 5 November 1953, and running for 132 performances.