You're right. Her mother is Hyppolyta, queen of the Amazons. I guess she's hot and Zeus banged her. A lot of the gods from Greek mythology had children with mortals. Hercules, Achilles, Gilgamesh, etc. are all half human.
Zeus is a
fictional deity in the
DC Comics universe, an interpretation of
Zeus from
Greek mythology. His appearances are most significant in stories of
Wonder Woman (Princess Diana). With the 2011 relaunch of DC Comics dubbed
The New 52, Zeus has received a prominent role in the Wonder Woman mythos, as he is now the biological father of Wonder Woman through
Hippolyta.
You made me do a little digging to make sure I wasn't full of... excrement, lol. I was pretty close.