Casla (Costello or Costelloe) is a Gaeltacht village between Indreabhán (Inverin) and An Cheathrú Rua (Carraroe) in western County Galway, Ireland. It lies on the R336 road beside Clynagh Bay. Casla is the headquarters of RTÉ Raidió na Gaeltachta. Casla means "(twisting) creek" or "inlet from the sea" in Irish.
It is served by Bus Éireann route 424 from Galway City.
In the novel The Wind Changes by Olivia Manning, set among the Irish independence fighters in 1921, Riordan, the last of the Easter Week leaders, is to land at Costello pier.