Maynooth Castle is a castle in Maynooth, County Kildare, Ireland.
The castle was built before the middle of the thirteenth century and was the home of the Fitzgerald family from 1176 until the 1534 rebellion of Silken Thomas, the son of the ninth Earl of Kildare. An English force led by William Skeffington bombarded the massive castle in March 1535, the heavy modern siege guns of the English army making a ruin of much of the Medieval structure. The Castle fell after a ten day siege. The garrison was subsequently executed.
Today the partly-ruined building remains as a tourist attraction, with limited access possible.
The Castle is situated at the entrance to the South Campus of NUI Maynooth.