Sigdal is a municipality in Buskerud county, Norway. The administrative centre of the municipality is the village of Prestfoss.
The municipality of Sigdal was established on 1 January 1838 (see formannskapsdistrikt). The area of Krødsherad was separated from Sigdal on 1 January 1901. The municipality has common borders with the municipalities of Flå, Krødsherad, Modum, Øvre Eiker, Flesberg, Rollag, and Nore og Uvdal.