"Casey at the Bat: A Ballad of the Republic, Sung in the Year 1888" is a mock-heroic poem written in 1888 by Ernest Thayer. It was first published anonymously in The San Francisco Examiner on June 3, 1888, under the pen name "Phin", based on Thayer's college nickname, "Phinney". Featuring a dramatic narrative about a baseball game, the poem was later popularized by DeWolf Hopper in many vaudeville performances. It has become one of the best-known poems in American literature.

Ernest Lawrence Thayer was an American writer and poet who wrote the poem "Casey", which is "the single most famous baseball poem ever written" according to the Baseball Almanac, and "the nation’s best-known piece of comic verse—a ballad that began a native legend as colorful and permanent as that of Johnny Appleseed or Paul Bunyan."