Old Deuteronomy is a character in T. S. Eliot's 1939 Old Possum's Book of Practical Cats and its 1981 musical adaptation, Cats. He is a wise and beloved elderly cat, further serving as the Jellicle patriarch in the musical. The role of Old Deuteronomy originated by Brian Blessed in the West End in 1981, and by Ken Page on Broadway in 1982. Judi Dench plays Old Deuteronomy in the 2019 film adaptation.

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.