The Aucilla River rises in Brooks County, Georgia, USA, close to Thomasville, and passes through the Big Bend region of Florida, emptying into the Gulf of Mexico at Apalachee Bay. Some early maps called it the Ocilla River. It is 89 miles (143 km) long and has a drainage basin of 747 square miles (1,930 km2). Tributaries include the and Wacissa Rivers. In Florida, the Aucilla River forms the eastern border of Jefferson County, separating it from Madison County on the northern part, and from Taylor County to the south.