Caravaggio painted two versions of Medusa, the first in 1596 and the other presumably in 1597.
The first version is also known as Murtula, by the name of the poet who wrote about it, Gaspare Murtola (d. 1624): "Flee, for if your eyes are petrified in amazement, she will turn you to stone." It measures 48 by 55 cm and is signed Michel A F (Latin: Michel Angelo Fecit), "Michel Angelo made [this]", Michelangelo being Caravaggio's first name. This work is privately owned.
The second version, shown here, is slightly bigger (60×55 cm) and is not signed; it is held in the Uffizi Gallery in Florence.