Lettermullan, (Irish: Leitir Mealláin, meaning "Mealláin's rough hillside" or possibly "the hill with the mill"), is a small island and village on the coast of Connemara in County Galway, Ireland. It is about 36 miles west of Galway city, at the far western end of Galway Bay, Lettermullen is the westernmost of three islands; Lettermullen, Gorumna and Lettermore, along with smaller islands collectively known as Ceantar na nOileán connected to the mainland by bridges and causeways.
Lettermullen is part of the Gaeltacht (Irish-speaking region) and Irish is the language most commonly spoken. Accordingly, its official name is Leitir Mealláin.
Lettermullen is connected to the islands of Dinish, Furnish, Inisherk and An Crappagh.