The parish is located at latitude 18°12'N, longitude 77°28'W. It is bordered on the south by Clarendon and Saint Catherine in the east by Saint Mary, and Trelawny, in the west. As with all but one parish, its coast is washed by the Caribbean sea. St. Ann covers an area of 1,212.6 km², making it the largest parish, before Saint Elizabeth's 1,212.4 km2. The population was an estimated 168,726 in 2001, with 11,066 living in the capital, St Anns Bay. Other important towns located in St. Ann are Discovery Bay, Brown's Town and Ocho Rios.
The highest elevation in the parish is in the Dry Harbour Mountains at 762 metres above sea level. Because of its limestone formation, the parish is noted for its 59 caves and numerous sinkholes. The Moneague Lake, which varies considerably in size, is one of the few large intermittent lakes in the island. The boundary between St Ann and St Mary is formed by the White River, which flows for 27.4 kilometres. Other rivers like the Dunns River appear intermittently, rising a few kilometres from the coast. The names of the main rivers are Negro, St Ann, Great, Roaring, Cave and Pedro
