St. Marys is a civil parish in County Westmeath, Ireland. It is located about 38.96 kilometres (24 mi) west–south–west of Mullingar. St. Mary's is the sole civil parish in the barony of Brawny in the Province of Leinster. The civil parish covers 12,069.4 acres (48.843 km2). The neighbouring civil parishes are: Kilkenny West to the north, Ballyloughloe to the east, Kilcleagh to the south–east and St. Peter's (County Roscommon) to the west.