Greek mythology, Scylla[a] (/ˈsɪlə/ SIL-ə; Greek: Σκύλλα, pronounced [skýl̚la], Skylla) is a legendary monster who lives on one side of a narrow channel of water, opposite her counterpart Charybdis. The two sides of the strait are within an arrow's range of each other—so close that sailors attempting to avoid Charybdis would pass dangerously close to Scylla and vice versa.
Scylla is first attested in Homer's Odyssey, where Odysseus and his crew encounter her and Charybdis on their travels. Later myth provides an origin story as a beautiful nymph who gets turned into a monster.
The strait where Scylla dwells has been associated with the Strait of Messina between Calabria, a region of Southern Italy, and Sicily. For example, as in Book Three of Virgil's Aeneid. The coastal town of Scilla in Calabria takes its name from the mythological figure of Scylla and it is said to be the home of the nymph.
The idiom "between Scylla and Charybdis" has come to mean being forced to choose between two similarly dangerous situations