Threecastles Castle is a three-storey tower house situated near Blessington, County Wicklow, Ireland.

Threecastles Castle is a rectangular three-storey tower house, with a stair turret projecting from the north east corner.

The castle was built on an east facing slope overlooking a ford on the River Liffey, where stepping stones crossing the river were also marked on an early 20th century map.

Much of the area south of the castle is now a flat marsh leading to the lakeshore.

It was probably built by Lord Deputy Gerald Fitzgerald, 8th earl of Kildare, in the 16th century.