Rennesøy is an island in Stavanger municipality in Rogaland county, Norway.

The islands of Mosterøy, Klosterøy, and Åmøy lie to the south and Finnøy and Talgje lie to the northeast.

The villages of Vikevåg and Sørbø are both located on the island.

Since 1992, the island is connected to the mainland city of Stavanger by a series of bridges and tunnels that are part of the European route E39 highway: the Mastrafjord Tunnel, the Askjesund Bridge, and the Byfjord Tunnel.

The western part of the island is relatively flat and well cultivated.