Mels is a municipality in the Wahlkreis (constituency) of Sarganserland in the Seeztal , Canton of St. Gallen , Switzerland .

Mels is first mentioned in 765 as Maile though this comes from a later copy of the original document. In 1018 it was mentioned as Meilis.

Mels has an area, as of 2006, of 139.2 km2 (53.7 sq mi). Of this area, 42.6% is used for agricultural purposes, while 29.3% is forested.