Toggenburg is a region of Switzerland. It corresponds to the upper valley of the River Thur and that of the Necker, one of its afluents. Since 1 January 2003, Toggenburg has been a constituency (Wahlkreis) of the canton of St. Gallen (SFOS number 1727).

The valley descends in a northwestern direction from the watershed between the Rhine and the Thur, and is enclosed on the northeast by the chain of the Säntis (8,216 ft [2,504 m]) and on the southwest by that of the Churfirsten (7,566 ft [2,306 m]) and of the Speer (6,411 ft [1,954 m]). It is a fertile valley of about 45 kilometres (28 mi) in length from the source of the river to Wil.