Supply Reef is a submerged circular reef of volcanic origin in the Northern Mariana Islands chain, about 10 kilometres (6 mi) NW of the Maug Islands. Presently this igneous seamount is roughly 8 metres (26 ft) below the ocean's surface and about 100 m (300 ft) in diameter. Apparent episodes of submarine volcanism were noted on December 22–24 and 26–27 in 1989.
|Summit depth||−8 m (−26 ft)|
|Location||Northern Mariana Islands|
|Last eruption||September to December 1989|