Aldabra, UNESCO World Heritage Site atoll in Seychelles.

Aldabra is an atoll in the Indian Ocean made up of four main islands surrounding a central lagoon filled with coral reefs, mangrove forests, and seagrass beds. The shallow waters and remote location have created a self-contained world where life has developed in ways found nowhere else.

Arab seafarers named the atoll Al-Hadra or Al-Khadra for its harsh, sun-baked environment, and Portuguese navigators visited it in 1511. In the mid-18th century it became a dependency of French Réunion, whose expeditions captured giant tortoises; Britain took possession in 1810. A settlement followed in 1888, and after the 1960s "Aldabra Affair" scuttled a planned RAF base, the Royal Society leased the atoll in 1970 and the Seychelles Islands Foundation took over management in 1979.

The name Aldabra probably comes from the Arabic al-Khadra, "the Green", for the lagoon's water; Portuguese charts of the 16th century called it Ilha Dara. The atoll has no permanent population, only reserve staff, scientists and a few fishermen, and since 2016 twelve inhabitants. On Picard Island stand the ruins of the 1888 settlement: a chapel built among badamier trees, water tanks, a two-room jail and a cemetery of Chinese workers.

Access is by boat from Mahé, about 1,120 km to the northeast, and only with permission from the Seychelles Islands Foundation, which manages the atoll; visitors stay aboard ship and land with reserve wardens. There is no surface freshwater and no facilities beyond the research station on Picard Island. Tides of two to three metres and currents over 11 km/h in the Grande Passe, between Picard and Polymnie, shape landing times.

The atoll is home to the largest population of giant tortoises in the region, animals that live for many decades and shape the character of the islands. These creatures are found almost nowhere else on Earth, making this place their most important refuge.