The island Aspronisi (meaning: the "white island") or Strogili is a small rocky and uninhabited island in the Cyclades. The island lies just west of Santorini and the Kameni islands and south of Thirassia. The island is part of the Santorini caldera that has emerged following the volcanic eruption in 1450 BC.

The dry island of Aspronisi has an area of 0.14 km2 and is 650 meters long and 200 meters wide. The island steeply rises out from the sea, is relatively flat (about 50% of the island is really flat) and has a height of 70 meters. Like the island of Santorini you can well see the layers here from which the island consists. The lower part of Aspronisi consists of dark lava and the white upper part of Aspronisi from pumice that descended after the volcano eruption.

The island Aspronisi has one small harbor and two pebble beaches but since there are no real sights and no people live here, is not visited by the island ferries and excursion boats. The island is privately owned by the same family for the last 7 generations. There is no electricity or water supply on Aspronisi.