This article is about the town in Ireland. There is also a suburb of Melbourne, Australia named Thomastown.

Thomastown (Baile Mhic Andáin in Irish) is a town in County Kilkenny, Republic of Ireland, south of Kilkenny city in the southeast of Ireland. Located along the River Nore, the town is the biggest in the county outside of Kilkenny city. Thomastown was called Grennan until the 11th century, at which time a Norman lord named Thomas took ownership of the town. The 12th century Jerpoint Abbey is located near the town.

The N9 Dublin–Waterford road passes through Thomastown, and the town is connected to the Irish railway network on the Dublin–Kilkenny–Waterford line.

See also: List of towns in the Republic of Ireland