Sumisu Island (須美寿島, Sumisu-tō) is a volcanic, deserted island located in the Philippine Sea approximately 110 kilometres (68 mi) off the coast of Aogashima, near the southern end of the Izu archipelago, Japan.

Due to its shape and heavy seas it is difficult to disembark on the island, although at times fishermen are known to have landed there.

In 1870, a submarine eruption was recorded NNE of the island, resulting in the formation of a new islet, named Niijima (新島), with a height of 13 metres (43 ft).

The islet has subsequently sunk beneath sea level due to erosion.

In November 1991, a fishing vessel reported that a large section of the island's northern face had collapsed, resulting in a significant change in its profile.