The Thouet starts in the "Gâtine" plateau, west of the Deux-Sèvres department, in the "commune" of Le Beugnon, near Secondigny and close to the source of the Sèvre Nantaise river, at an elevation of about . From the source to Parthenay the river flows in a generally southwest-northwest direction. To the east of Parthenay, the river turns north and flows on a generally northward direction for the rest of its course.