Middelharnis is a town located in the western Netherlands within the province of South Holland. It is situated on the island of Goeree-Overflakkee.
As of 2012, the town had a population of approximately 6,800 residents. On January 1, 2013, Middelharnis merged with the communities of Goedereede, Dirksland, and Oostflakkee to form the new municipality of Goeree-Overflakkee.