Until 1 January 2007 Søndersø municipality was a municipality (Danish, kommune) in the former Funen County on the island of Funen in central Denmark.
The municipality covered an area of 181 km2, and had a total population of 11,234 (2005).
Its last mayor was Erik Hansen, a member of the Social Democrats (Socialdemokraterne) political party.
This created a municipality with an area of 451 km2 and a total population of 28,655 (2005).
The new municipality belongs to Region of Southern Denmark.