The municipality of Melhus includes the valley of the river Gaula as it flows northwards towards its mouth at the Gaulosen, an arm of the Trondheimsfjord. The lake Svorksjøen lies on the western border with Orkdal and Meldal. The lakes Benna and Ånøya lie in the central part of the municipality, and the lake Samsjøen lies on the southeastern border with Midtre Gauldal municipality. The mountains of Rensfjellet and Vassfjellet lie on the eastern border with Selbu and Klæbu municipalities, respectively.