Nengonengo, Atoll in Tuamotu Archipelago, French Polynesia

Nengonengo stretches 13 kilometers in length with a bell-shaped configuration, encompassing a 67-square-kilometer lagoon accessible through a narrow northern pass that allows limited vessel navigation.

First encountered by European explorer Samuel Wallis in 1767 who named it Prince William Henry, this remote atoll remained largely unexplored until detailed nautical surveys were conducted in 1952.

The atoll is no longer permanently inhabited; its only activity is pearl farming, with cultivation and grafting authorised on 500 hectares of the lagoon. The pearl company of Robert Wan owns the atoll and its airfield, and the atoll belongs to the commune of Hao together with Ahunui, Manuhangi and Paraoa.

Access requires careful navigation through shallow passages with tidal restrictions, while a small airstrip constructed in 1993 provides essential logistical connections for residents and commercial pearl farming operations.

The atoll sits atop a submarine volcano 4,355 metres tall, formed roughly 45.8 to 47.6 million years ago and holding a volume of about 4,744 km3, one of the highest such mountains in the Tuamotu chain. Its reef rises only about 45 metres above that summit.