Hippolyte was reportedly a daughter of Ares, god of War and a queen of the Amazons. Her mother is named Otrera by Hyginus. Thus making her a full sister of Penthesilia. Her name derives from the Greek words "hippos" ( ἵππος) for "horse", and "lyo" (λύω) for "setting loose, unleash" or "severe". The literal meaning of the name being "Unleasher of Horses".
According to her legend, Hippolyte held possession of a girdle (belt) granted to her by her father. It was created by the Gods and symbolized her supremacy. Admete, the young daughter of Eurystheus, King of Mycenae, heard of the item and wished to possess it. So her father assigned Heracles to fetch it for her. Heracles had to organize an entire campaign against the Amazons, joined by several heroes. most notably Theseus of Athens.
According to some versions, Hippolyte welcomed the strangers and tried to resolve the matter peacefully. She was willing to part with the girdle, either to avoid bloodshed or in exchange for a one-night-stand with Heracles. But her paternal grandmother Hera had a different opinion. She convinced the Amazons that the visitors were planning to betray them. Resulting in a battle between the two groups. Depending on the version, Hippolyre was either killed or captured in the battle. Heracles returning to Mycenae with the girdle.
In another version, Heracles simply resorted to blackmail. Capturing Melanippe, a sister of Hippolyte, and exchanging her life for the girdle. Note that the two sister are often identified with each other.
Some versions end her story there. Others continue with tales of Theseus. Theseus returned to Athens with an Amazon captive. Either Hippolyte or her sister Antiope. Either way, the two sisters are identified with each other and their legends are identical. All versions agree that Theseus and his new wife/concubine had a son: Hippolytus. Himself famous for being the prize in a conflict between Aphrodite and Artemis.
From there different sources conclude the tale in different ways:
Version #1: Hippolyte/Antiope died of natural causes, possibly in childbirth. Theseus proceeded to marry Phaedra, Princess of Crete.
Version #2: Theseus got tired of Hippolyte/Antiope and exiled her. She died of a broken heart in Megara, not far from Athens.
Version #3: Theseus married Hippolyte/Antiope and lived with her for a while. But then deserted her in favor of Phaedra. The scorned Hippolyte contacted her Amazons and interrupted Theseus' new wedding ceremony with an invasion force. A battle took place. Hippolyte loosing her life at the hands of Theseus.
Version #4: Closely follows Version #3. But Hippolyte/Antiope looses her life in a friendly fire incident at the hands of Penthesilia.
Version #5: Theseus and Hippolyte/Antiope are happily married. But the Amazons invade Attica in an attempt to retrieve their Queen. The couple team-up to face the invasion force. The Queen of Athens looses her life at the hands of Molpadia, a fellow Amazon.