Errew Abbey is a former Augustinian monastery and National Monument located in County Mayo, Ireland.

In 1413 the Barretts founded an abbey for the Augustinian Canons, dedicated to the Virgin Mary; they seem to have made use of the buildings from the earlier foundation.

Saint Tigernan is said to have appeared to McWattin every night until he promised to make amends; he gave the abbey an éraic of a quarter of land (ceathrú mír, about 120 acres) at Ballinbraher (Friarstown).

[citation needed] A family called O'Flynn were erenachs of the lands at Errew and came into the possession of Mias Tighernain, a paten said to have belonged to Tigernan.

[citation needed] There is a long rectangular church, measuring 27 × 7 m (90' by 22') which has retained some trefoil-headed windows, two sedilia and a piscina.