"Gus: The Theatre Cat" is a poem by T. S. Eliot included in Old Possum's Book of Practical Cats. Known as "The Theatre Cat" due to his career as an actor, Gus is an old and frail, yet revered, cat, who "suffers from palsy, which makes his paws shake." His coat is described as "shabby" and he is "no longer a terror to mice or to rats."

Old Possum's Book of Practical Cats (1939) is a collection of whimsical light poems by T. S. Eliot about feline psychology and sociology, published by Faber and Faber. It serves as the basis for Andrew Lloyd Webber's 1981 musical Cats.