St. Elmo is a novel by American author Augusta Jane Evans published in 1866. Featuring the sexual tension between the protagonist St. Elmo, a cynical man, and the heroine Edna Earl, a beautiful and devout girl, the novel became one of the most popular novels of the 19th century. The novel sold a million copies within four months of its publication.

The novel St. Elmo was frequently adapted for both the stage and screen. It inspired the naming of towns, hotels, steamboats, and a cigar brand. The book's heroine Edna Earl became the namesake of Eudora Welty's heroine (Edna Earle Ponder) in The Ponder Heart published in 1955.