Mombasa Island is a 5 km by 3 km coral outcrop located on Kenya's coast on the Indian Ocean.

The old town of Mombasa is located at the eastern, seaward end of the island. Kilindini and Port Reitz, the modern deep water harbour and port separates the island from the African mainland to the south. The old harbour, which is named Port Tudor and guarded by Fort Jesus, and Tudor Creek separate the island from the northern mainland. Modern residential sprawl and industrial areas now occupy the rest of the island.

Mombasa is linked to the mainland by the Makupa Causeway to the west, by the Nyali Bridge to the north and by the Likoni Ferry to the south.

Port Tudor and Tudor Creek were named by Owen Tudor the Royal Navy captain who first surveyed the area.