Aspronisi (Greek: Ασπρονήσι) is an uninhabited island lying within the Santorini caldera.

[1] The island was originally formed by the massive Minoan eruption in the 2nd millennium BC, after which it was gradually built up by successive volcanic activity.

[3][4] Aspronisi was formed through the gradual volcanic activity in Santorini caldera, which itself is composed of four distinct shield volcanoes.

[5] The island was formed along with the current Santorini caldera during a massive eruption in the 2nd millennium BC that expelled 14 cubic miles (60 km3 ) of dense rock.

[4][3] The island is dominated by steep cliffs, making landings difficult, though two pebble beaches and a small anchorage exist on the islet.