Helen is the most beautiful woman to ever strut her stuff across the face of the earth. Too bad all that allure ever does is get her and everybody around her in tons of trouble. When she ditches her husband, Menelaus, to run away with Paris, the pretty boy of Troy, she helps to ignite the awful Trojan War. Forever after, she'd dubbed "the face that launched a thousand ships" because of the huge Greek fleet that sailed to Troy to reclaim her.
Like her boy toy, Paris, Helen still has a pretty bad reputation to this day. Though no one disputes her beauty, she's often depicted as being ditzy, unfaithful, and totally self-centered. Some versions of the story (especially more modern ones) put her in a slightly better light, however. In some tellings of the tale, Paris kidnaps her, and she doesn't go to Troy of her own free will. Some variations also emphasize that Menelaus was a major jerk, who cheated on her all the time (not that anybody would've cared about that in ancient Greece).