Umboi (also named Rooke or Siassi) is a volcanic island between the mainland of Papua New Guinea and the island of New Britain. It is separated from New Britain by Dampier Strait and Huon Peninsula, New Guinea Island by Vitiaz Strait. It has an elevation of 1,548 m. Umboi is a Holocene complex volcano with no historic eruptions. A complex volcano refers to the extensive assemblage of spatially, temporally, and genetically related major and minor volcanic centers with their associated lava and pyroclastic flows.