When We Were Twenty-One is a 1915 American silent comedy film directed by Hugh Ford and Edwin S. Porter and written by H.V.

The film stars William Elliott, Charles Waldron, Marie Empress, Helen Lutrell, Winifred Allen, and Arthur Hoops.

In a mock ceremony, the four guardians betroth Richard to Phyllis, the baby daughter of the housekeeper, Mrs. Ericson.

Nicknamed "The Imp" because of his fondness for pranks, Richard grows to be athletic and handsome.

Richard soon becomes infatuated with a dancer known as "The Firefly," who, after hearing a rumor that he will inherit a fortune when he turns twenty-one, entices him to marry her.