A township in south-central Ontario, Canada, in the County of Simcoe. It was created in 1993 when the County of Simcoe Act merged the townships of Adjala and Tosorontio. The amalgamation took effect on January 1, 1994. “Tosorontio” is a Huron word meaning “Beautiful Mountain”, and Adjala was the name of the wife of Chief Tecumseh, for whom the neighbouring township (now called New Tecumseth) was named.
A predominantly rural area, Adjala–Tosorontio contains numerous small villages and hamlets. Many communities were started in Adjala by Irish Catholics who named their hamlets after their home towns in Ireland, or after prominent pioneer families who first settled the area. The township comprises the communities of Achill, Airlie, Athlone, Ballycroy, Cedarville, Colgan, Connor, Everett, Glencairn, Hockley, Keenansville, Lisle, Loretto, Rosemont, Sheldon, Tioga and Tuam.
The municipality has increasingly become home to residents who commute to the Greater Toronto Area.
Geographically the area is rolling countryside below the Niagara Escarpment to the west, with the Nottawasaga River cutting through it.