Guldborgsund Municipality is a kommune in the Region Sjælland of Denmark, created on 1 January 2007 from six (6) former municipalities on the two islands Lolland in the west and Falster in the east bordering the Guldborgsund strait. It covers an area of 903.15 km2 (2013) and has a total population of 60,231. Its neighboring municipalities are Lolland to the west and Vordingborg to the north. Its administrative seat is in the town of Nykøbing Falster. Its mayor as of 1 January 2022 is Simon Hansen, representing the Social Democrats.

Sakskøbing, previously spelled Sakskjøbing, is a town on the island of Lolland in south Denmark. It has a population of 4,590. Until 1 January 2007 it was the seat of the former Sakskøbing Municipality, and is now situated in Guldborgsund Municipality in Region Sjælland.