In Clash of the Titans, Gemma Arterton plays Io, a demi-goddess who is the love interest to Sam Worthington's Perseus. Having taken two classes of Greek Mythology in college, I am ashamed to admit that I cannot remember Io. According to Wikipedia, the goddess is known for a collection of shenanigans with the jealous Hera, but fails to mention anything on her relationship with Perseus.
If you don't recognize Arterton, then you definitely didn't see Quantum of Solace, where she played MI6 agent Strawberry Fields. Though this picture doesn't do her justice, she is without a doubt a hottie.
Update: Ozzy sent over this clarification of the goddess.
If you look into greek mythology though, you’ll find that Io was a priestess of Hera who was seduced by Zeus. Nowhere does it mention her being romantically linked to Perseus and this would be disgusting if not impossible since Perseus is a descendant of Io. That said, Perseus’ love interest is Andromeda (who is played Alexa Davalos in the 2010 remake of Clash of the Titans), daughter of Cepheus and Cassiopeia. She was chained to a rock as a sacrifice to a sea monster and was saved by Perseus. Incidentally, the original 1981 film also has Andromeda as Perseus’ love interest, and not Io.
Clash of the Titans
Clash of the Titans opens to theaters March 26th, 2010.