Until January 1, 2007 Ramsø was a municipality (Danish, kommune) in the former Roskilde County on the island of Zealand (Sjælland) in east Denmark. The municipality covered an area of 76 km², and had a total population of 9,320 (2005). Its last mayor was Poul Lindor Nielsen, a member of the Social Democrats (Socialdemokraterne) political party. The main town and the site of its municipal council was the town of Viby. Other towns and villages in the municipality were Gadstrup, Skalstrup, Snoldelev and Ørsted.
The municipality was created in 1970 due to a kommunalreform ("municipality reform") that combined a number of existing parishes:
- Dåstrup Parish
- Gadstrup Parish
- Snoldelev Parish
- Syv Parish
- Ørsted Parish
Ramsø municipality ceased to exist as the result of Kommunalreformen ("The Municipality Reform" of 2007). It was merged with the existing Gundsø and Roskilde municipalities to form the new Roskilde municipality, which created a municipality with an area of 212 km² and a total population of 79,441 (2005). The new municipality belongs to Region Sjælland ("Zealand Region").