Frank Sydney Box (29 April 1907 – 25 May 1983) was a British film producer and screenwriter, and brother of British film producer Betty Box. In 1940, he founded the documentary film company Verity Films with Jay Lewis. He produced and co-wrote the screenplay, with his then wife Muriel Box, for The Seventh Veil (1945), which received the 1946 Oscar for best original screenplay. Sydney and Muriel married in 1935, had a daughter Leonora, the following year and divorced in 1969.