Motu One, also known as Bellinghausen, is an atoll in the Leeward group of the Society Islands, in the South Pacific.

Motu One's reef encloses totally a lagoon without a pass.

Motu One means Sand Island in Tahitian, that is a low-lying, sandy islet that cannot sustain permanent human habitation.

The name Atoll Bellinghausen or more rarely Bellingshausen was given to this small atoll by Otto von Kotzebue, an officer and navigator of Baltic German descent in the Imperial Russian Navy, in honour of Fabian Gottlieb von Bellingshausen.

The atoll was visited by the US Exploring Expedition in Sept.