Warning: Spoilers follow
The film is about a convict who escapes prison and brings along two fellow prisoners with the promise of a treasure. The man's wife is about to remarry and the three characters trek towards the man's home. The film stars George Clooney, John Turturro, Tim Blake Nelson, John Goodman, and Holly Hunter. The Coen brothers claim to have based on The Odyssey by Homer but admit to not having read the poem. The film's American roots music soundtrack became a surprise hit, and won a Grammy for Album of the Year. (See O Brother, Where Art Thou? soundtrack.)
The title of the film is a reference to a satirical 1941 film, directed by Preston Sturges, called Sullivan's Travels, where a director wants to direct a film called O Brother, Where Art Thou? but is being forced to direct another film instead; the director wants to experience poverty and keeps trying to but is constantly returned to his posh surroundings. This director's experience is the opposite of that of Odysseus in The Odyssey--Odysseus wants to return home and is constantly being diverted from it.