Queen Hippolyte (also spelled Hippolyta) was the daughter of Ares, the Greek god of war, and Otrera. She was the queen of the Amazons. Her father had given her, as a symbol of her authority, his own girdle/belt. Her name meant "unbridled mare".
Admeta, the daughter of king Eurystheus, wanted the girdle of queen Hippolyte and so this endeavour became the 9th labour of Herakles.
There are several versions about how Herakles got the girdle:
In Pseudo-Hyginus, Herakles just killed Hippolyte and got the girdle, and then he took Antiope, her sister, whom he gave as a present to Theseus.
In another version, Herakles kidnapped Melanippe, Hippolyte's sister, and so the queen agreed to give him the girdle in exchange for the freedom of Melanippe.
There is also another version in which queen Hippolite agreed to give Herakles her girdle, but he didn't trust her, that's why he killed her and took the girdle.
But we haven't finished yet: in another version, she gave him the girdle, but Hera, who was Herakles' enemy, disguised herself as an Amazon and told the others that Herakles couldn't be trusted. A fight between the Amazons and Herakles' men followed, and queen Hippolyte was killed. Herakles was very sad about this, because he intended to marry her.
Luckily enough, there are also versione in which she does not die so soon.
In Apollodorus, Hyppolite had a son, Hyppolitus, with the hero Theseus. It is said that Theseus came to the land of the Amazons and was well received by them. The queen herself went aboard his ship, in order to bring him welcome gifts, but he just kidnapped her and made her his bride. They has a son, Hippolytus.
After a while, Theseus fell in love with Phaedra and decided to marry her. Hippolyte was so enraged, that she crashed the wedding with her Amazons, threatening to kill all the guests. A battle started and she was killed either by mistake, by her own sister/ally Penthesileia, or by Theseus himself, or by his men, who bolted the doors, locked her inside and then killed her.
I'll finaly mention another version in which Theseus was not such a jerk as to leave her (he surely knew a thing or two about leaving girls), because she just died and was buried in a tomb shaped like an Amazons' shield.