The Legend of Meenakshi (sometimes spelled Minakshi)
Long ago in Madurai, India, there lived a King and Queen. The couple was childless and the King was in need of an heir. He prayed and performed a sacrifice in order to obtain a son but out of the sacrificial fire came a young girl with three nipples. She was Meenakshi, the Fish-Eyed incarnation of Parvati. The King was dismayed at not getting a son and further dismayed at getting a daughter with an abnormality. But a divine voice said, "Consider this girl to be your heir and train her like you would your son. As for her third breast, it will disappear when she meets her future husband."
In due course Meenakshi was crowned ruler of Madurai and she embarked on a program of expansion, conquering many kingdoms in her northward advance. When she reached Kailash Mountain, the home of Shiva, she destroyed Shiva's army so quickly that Shiva was compelled to enter the fray himself. For a moment the adversaries stood face to face and then Meenakshi's third breast disappeared. She threw down her weapons and surrendered to her husband to be.
Links to other versions:
Here, here, and here. There is also the Wikipedia entry on Meenakshi.