Prasonisi of Lefki is a small, uninhabited islet located in the southeastern part of Crete, very close to the island of Lefki (Koufonisi), south of Sitia and off the coast near Goudouras. It belongs to the cluster of islets that surround Lefki in the Libyan Sea.

Its name is associated with the sparse yet noticeable vegetation that appears in parts of the islet, giving it a subtle greenish hue within an otherwise arid landscape. Its morphology is mainly rocky, with gentle elevation changes and a coastline that alternates between rough and smoother formations.

The islet forms part of an area of significant ecological importance, as Lefki and its surrounding islets host rare species of flora and fauna, as well as important seabird populations. Its isolation and the absence of human activity have helped preserve its natural character.

Access to Prasonisi is possible only by sea, typically from the southern coast of Crete, and there are no facilities or infrastructure. Despite its small size, it is part of a distinctive island landscape that highlights the wild and authentic character of southeastern Crete.