Assumption Island is a small island located at 9°45′S 46°29′E in the Indian Ocean north of Madagascar and is part of the country of the Seychelles. It is located about 30 km southeast of the Aldabra Atoll and is part of the Aldabra Group. It is a single coral island which measures 11.07 km² in area and which has a small settlement on the sheltered western side, surrounded by Casuarina trees. An abandoned coconut palm plantation is just south of it. There is a concrete runway that runs from between the two sand dunes on the southeast to the settlement. The western shore features an almost uninterruptend sandy beach of 5 km. Two large sand dunes are prominent on the southeastern coast of the island, one of them 32 m high.
Due to the devastating effect of guano mining which lasted until 1983, the island is dominated by expanses of bare rock and caves, and is sparsely covered with low-growing vegetation.
A notable feature of this island is the Assumption Island day gecko, a subspecies of gecko found only on this island.
The documentary The Silent World was partially shot on Assumption.