The Canton of Thurgau (German: , anglicized as Thurgovia) is a northeast canton of Switzerland. It is named for the Thur River, and the name Thurgovia was historically used for a larger area, including part of this river's basin upstream of the modern canton. The area of what is now Thurgau was acquired as subject territories by the cantons of the Old Swiss Confederacy from the mid 15th century. Thurgau was first declared a canton in its own right at the formation of the Helvetic Republic in 1798.