Cahir ( Irish: Cathair Dhún Iascaigh, meaning the stonefort of the fishing, or An Chathair [6], "the stone fort"), often spelled Caher in older accounts, is a town in South Tipperary, Ireland. The town is best known for its castle and the Swiss cottage.

It was known for much of its history as being a defence town, and was one of the first towns to be linked by stagecoach in the nineteenth century, when Charles Bianconi commenced services between Clonmel, Cahir and Cashel. The building at The Square, where The Galtee Inn is now sited, was the stopping point in the town for Bianconi's coaches.