Donald Esme Clayton Calthrop (11 April 1888 – 15 July 1940) was an English stage and film actor.Born in London, Calthrop was educated at St Paul's School and made his first stage appearance at eighteen years of age at the Comedy Theatre, London. His first film was The Gay Lord Quex released in 1917. He starred as the title character in the successful musical The Boy in the same year. He then appeared in more than 60 films between 1916 and 1940, including five films directed by Alfred Hitchcock.

He died in Eton, Berkshire from a heart attack while he was filming Major Barbara (1941). According to Ronald Neame in his autobiography, some shots in the final film had a stand-in playing Calthrop's role (from the back) and a piece of dialogue was recorded using an unnamed person who impersonated Calthrop's voice.

He was the nephew of dramatist Dion Boucicault.