| Sumisu Island | |
| Native Name: | Sumisu-tō (須美寿島) |
| Location: | Izu Islands |
| Archipelago: | Izu Islands |
| Area M2: | 30000 |
| Elevation M: | 134 |
| Country: | Japan |
| Country Admin Divisions Title: | Prefecture |
| Country Admin Divisions: | Tokyo |
| Country Admin Divisions Title 1: | Subprefecture |
| Country Admin Divisions 1: | Hachijō Subprefecture |
| Population: | 0 |
is a volcanic, deserted island located in the Philippine Sea approximately 110km (70miles) off the coast of Aogashima, near the southern end of the Izu archipelago, Japan. Sumisu-tō is administratively part of Tokyo Metropolis.
The island is a basalt and olivine pillar with sheer sides, the only visible portion of an active submarine volcanic caldera extending south of the island with a circumference of approximately . The above sea-level portion has a height of . The island is estimated to have been created by a volcanic eruption around 20,000 years ago. In the immediate vicinity are numerous exposed and awash rocks. 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. The abundance of fish in the surrounding waters has made it attractive for both sport and commercial fishing.
The island has been known by Japanese fishermen and mariners from an early time. In 1870, a submarine eruption was recorded NNE of the island, resulting in the formation of a new islet, named, with a height of . The islet has subsequently sunk beneath sea level due to erosion. From 1974 to 1977, a series of underwater eruptions have been recorded, discoloring water in the area. 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. Further changes to the island's profile were recorded after 1992 earthquakes.