The Seeztal is a valley of the canton of St. Gallen, Switzerland, extending to the east of Lake Walen for some 10 km, formed by the Seez river. The valley appears to be a left branch off the Rhine valley at Sargans, but there is a divide at Mels. Situated in the Seeztal are the municipalities of Walenstadt (425 m), Flums (453 m) and Mels (500 m).Running along the valley are the A3 motorway and the Chur-Zürich railway line.