The Mediterranean monk seal is a monk seal belonging to the family Phocidae. As of 2015, it is estimated that fewer than 700 individuals survive in three or four isolated subpopulations in the Mediterranean, (especially) in the Aegean Sea, the archipelago of Madeira and the Cabo Blanco area in the northeastern Atlantic Ocean. It is believed to be the world's rarest pinniped species. This is the only species in the genus Monachus.

The earless seals, phocids, or true seals are one of the three main groups of mammals within the seal lineage, Pinnipedia. All true seals are members of the family Phocidae. They are sometimes called crawling seals to distinguish them from the fur seals and sea lions of the family Otariidae. Seals live in the oceans of both hemispheres and, with the exception of the more tropical monk seals, are mostly confined to polar, subpolar, and temperate climates. The Baikal seal is the only species of exclusively freshwater seal.