Io (/aj. o/; Ancient Greek: 8 [iT]) was, in Greek mythology, one of the mortal lovers of Zeus. An Argive princess, she was an ancestor of many kings and heroes, such as Perseus, Cadmus, Heracles, Minos, Lynceus, Cepheus, and Danaus. The astronomer Simon Marius named a moon of Jupiter after Io in 1614.

Quick Facts. Io is named for a mythological woman transformed into a cow during a marital dispute between the Greek god Zeus  Jupiter in Roman mythology  and his wife, Juno.