At Swim-Two-Birds is a 1939 novel by Irish author Brian O'Nolan, writing under the pseudonym Flann O'Brien. It is widely considered to be O'Brien's masterpiece, and one of the most sophisticated examples of metafiction.
The novel's title derives from Snámh dá Én (Middle Ir.: "Swim-Two-Birds"), a ford on the River Shannon, between Clonmacnoise and Shannonbridge, reportedly visited by the legendary King Sweeney, a character in the novel.
The novel was included in TIME magazine's list of the 100 best English-language novels from 1923 to 2005.