Thorah Island is located in the southeast portion of Lake Simcoe, approximately four kilometres west from Beaverton, Ontario, Canada. The island, part of Brock Township, is approximately 1,450 acres (6 km²) in size and the land is divided mainly between wooded and wooded-swamp terrain. Some land has been cleared for farming and recreational purposes but much of the agricultural land has fallen into disuse and has grown over. Centre Road runs from the east side of the island to the west side but is not much more than a dirt path. A small harbour exists on the east side of the island, directly across from Beaverton Harbour.