St. Joseph Atoll, Coral atoll in Amirantes Group, Seychelles.

St. Joseph Atoll is an oval coral atoll about 7 km long and 4.4 km wide, with a total area of 22.53 km². Its 13 sandy islets cover only 1.39 km², while the enclosed lagoon reaches a maximum depth of 6.4 m. The main island, Saint Joseph, is a crescent-shaped coral sand cay 2.2 km long and nowhere higher than 3 m.

European sailors first came to the atoll in 1770 and it remained under private ownership for more than two centuries. In 2012 the islands changed hands and entered a new phase as a protected marine area.

The atoll's coconut plantations were established after a Seychellois family acquired the island in 1960. A small population of about ten people lived here before moving to D'Arros Island, and ruined buildings remain near the cultivated area at the western end of the main island.

The atoll is remote and accessible only by boat, requiring advance planning to reach from inhabited areas. Visitors should expect challenging sea conditions and limited landing facilities on the islands.

The lagoon has no growing reefs; at low water it drains over a narrow sill, Passe Lerein Fin, at its western end. Only there can small boats enter the lagoon at high tide. Depths of 500 m lie just 1.5 km east of the reef edge.