Grand Lake Saint Marys, reservoir, Mercer and Auglaize cos., W Ohio, on Beaver Creek, branch of Wabash R., 1 mi/1.6 km SE of Celina; 8 mi/12.9 km long, 3 mi/4.8 km wide. Formed by dams at E (40°31'N 84°25'W) and W (40°32'N 84°04'W) ends of lake; linked (E end) to St. Mary’s R. by 2-mi/3.2-km channel. Grand Lake–St. Marys Park at E end; fish hatchery.
