The Key is a 1958 British-American war film set in 1941 during the Battle of the Atlantic. It was based on the 1951 novel Stella by Jan de Hartog and was directed by Carol Reed. William Holden, Sophia Loren and Trevor Howard starred in the production.

Jan de Hartog was a Dutch playwright, novelist and occasional social critic who moved to the United States in the early 1960s and became a Quaker.