Kolbeinsey is a small islet in the Greenland Sea located 105 kilometres off the northern coast of Iceland, 74 km (40 nmi) north-northwest of the island of Grímsey. It is the northernmost point of Iceland and lies north of the Arctic Circle. The islet is named after Kolbeinn Sigmundsson, from Kolbeinsdalur in Skagafjörður, who according to Svarfdæla saga is said to have broken his ship there and died with his men.

An islet is a very small, often unnamed island. Most definitions are not precise, but some suggest that an islet has little or no vegetation and cannot support human habitation. It may be made of rock, sand and/or hard coral; may be permanent or tidal ; and may exist in the sea, lakes, rivers or any other sizeable bodies of water.