Aghalard Castle, Medieval tower house in County Mayo, Ireland

Aghalard Castle is a three-story stone tower in County Mayo, built with square corner turrets for defense. The structure was originally surrounded by a defensive wall called a bawn, which enclosed the entire complex within the Irish countryside.

Aghalard Castle was built around 1490 by descendants of the McDonnells of Knocknacloy, who had become gallowglass, or mercenary soldiers, for the Burkes of Mayo. In 1596 it was taken by Edward Brabazon, 1st Baron Ardee, Ulick Burke, 3rd Earl of Clanricarde and James Riabhach Darcy, but the castle was evacuated soon after when Hugh Roe O'Donnell approached. It stayed with the McDonnells until Sir Benjamin Guinness bought it in the 19th century.

The McDonnells of Knocknacloy came as gallowglass, mercenary soldiers serving the Burkes of Mayo, and their descendants built the castle around 1490. The Irish name Caisleán Achadh Leathard refers to the field or ford site. The ruin is listed as a National Monument.

The ruins are located on rural land south of Castlebar and can be reached via country roads. It is wise to wear sturdy footwear and approach the site carefully, especially during wet weather conditions.

Aghalard is recorded as a National Monument. In 1596 Edward Brabazon, 1st Baron Ardee, Ulick Burke, 3rd Earl of Clanricarde and James Riabhach Darcy took the castle, but left it soon after learning that Hugh Roe O'Donnell was approaching.