New Tecumseth is a town in Simcoe County, in south-central Ontario, Canada.

The municipality was created in 1991 through the amalgamation of the Town of Alliston, the Villages of Beeton and Tottenham, and the Township of Tecumseth.

The name 'New Tecumseth' was chosen because a Town of Tecumseh already existed in Essex County.

The main centres in New Tecumseth are the communities of Alliston, Tottenham, and Beeton.

The town also includes the smaller communities of Allimil, Green Briar, Nicolston, Penville, Randall, Rich Hill, Schomberg Heights and Thompsonville.