Oostflakkee (Dutch pronunciation: [ˌoːstflɑˈkeː] ⓘ) is a former municipality on the island of Goeree-Overflakkee in the western Netherlands, in the province of South Holland.

On January 1, 2013, Oostflakkee merged with Goedereede, Dirksland, and Middelharnis into the new municipality of Goeree-Overflakkee.

Oude Tonge was the main town of this former municipality and has a considerable industrial area.

A few kilometers east of Den Bommel there is Zuidzijde, a very small town with a neat looking watertower.

This town is the yearly start and finish of De Omloop - a 100+ km walk around the island in a 24-hour period.