Rennesøy is a municipality in Rogaland county, Norway. It is part of the region of Ryfylke. The administrative center is the village of Vikevåg. The parish of Rennesø was established as a municipality on 1 January 1838. Mosterøy was separated from Rennesøy on 1 July 1884. It was, however, merged back with Rennesøy on 1 January 1965.