Croom Castle, Medieval castle in Croom, Ireland

Croom Castle is a castle ruin on the bank of the River Maigue in County Limerick, Ireland. Two walls remain standing at roughly half their original height, rising directly above the water's edge.

The O'Donovan family built a fortress here in the early 13th century, and the FitzGeralds later took control and made it their main seat. That shift in ownership shaped the balance of power in this part of Limerick for a long time.

The FitzGerald family battle cry 'Crom a Boo' takes its name directly from the Irish name of this place. Visitors walking through the ruins can still feel how deeply this family tied their identity to the site.

The ruins sit on the bank of the River Maigue near the town of Croom, reached from the N20 road between Limerick and Charleville. Sturdy footwear is a good idea, as the ground around the old walls is uneven and can be slippery after rain.

The castle's name comes from the Irish cromadh, "bend in the river", after the sharp turn of the Maigue it guards. The same word gave the FitzGeralds their war cry Crom abú, "Croom forever", still shown on their coat of arms.