Kihnu is an island in the Baltic Sea. With an area of 16,4 km² it is the largest island in the Gulf of Riga and the seventh largest island of Estonia. The length of the island is 7 km and width 3.3 km, the highest point is at 8.9 m above sea level.
The island belongs to the Pärnu County of Estonia. Together with neighbouring islands it forms Kihnu Parish, one of the smallest municipalities of the country with an area of 16,8 km².
604 people live on Kihnu as of 2007 of whom 69 are primary school pupils. There are four villages: Lemsi, Linaküla, Rootsiküla and Sääre. One can reach Kihnu by plane from Pärnu (15 minutes) or ferry from either Pärnu (3 hours) or Manilaid (1 hour), and when the sea is frozen in winter it is possible to drive to the island over the ice.