Warren Casey (1935 - November 8, 1988) was an American theatre composer, lyricist, writer, and actor.

Born in Yonkers, New York, Casey received his Fine Arts Degree from the Syracuse University School of Visual and Performing Arts in 1957.

In the mid-1960s, Casey met Jim Jacobs while acting with the Chicago Stage Guild, and the two began collaborating on a play about high school life during the golden age of rock 'n' roll in the 1950s. Entitled Grease, it premiered in 1971 at the Kingston Mines Theater in the Old Town section of Chicago. Producers Ken Waissman and Maxine Fox saw the show and suggested to the playwrights that it might work better as a musical, and told them if the creative partners were willing to rework it and they liked the end result, they would produce it off-Broadway. Casey quit his day job as a department store lingerie buyer and the team headed to New York City to collaborate on what would become Grease, which opened at the Eden Theatre in downtown Manhattan, moved to Broadway, and earned him a Tony Award nomination for Best Book of a Musical. The show went on to become a West End hit, a hugely successful film (for which he and Jacobs wrote additional songs), and a staple of regional theatre, summer stock, community theatre, and high school drama groups. Casey's acting credits included the original production of David Mamet's Sexual Perversity in Chicago in 1974 at the Organic Theater Company. That same year, he fronted $1,000 to help start Victory Gardens Theater in Chicago.

Casey died of AIDS-related complications in Chicago at the age of 53. At the time of his death he was writing a musical with the Brazilian performer Valucha de Castro.