The Big Blockade was a 1942 British black-and-white war propaganda film in the style of dramatised documentary. It was directed by Charles Frend and starred Will Hay, Leslie Banks, Michael Redgrave and John Mills. It was produced by Michael Balcon for Ealing Studios, in collaboration with the Ministry of Economic Warfare.

William Thomson Hay was an English comedian who wrote and acted in a schoolmaster sketch that later transferred to the screen, where he also played other authority figures with comic failings. His film Oh, Mr. Porter! (1937), made by Gainsborough Pictures, is often cited as the supreme British-produced film-comedy, and in 1938 he was the third highest-grossing star in the UK. Many comedians have acknowledged him as a major influence. Hay was also a keen amateur astronomer.