The Greek goddess Themis is the one linked most often to the sign of Libra. Themis was one of the six 'daughters of heaven,' a product of merging Earth (Gaia) and Sky (Ouranos/Uranus), perhaps less a goddess and more the personification of law and order. While the astrological sign of Libra is known for its connection to law and the scales of justice, the origin of that connection has less to do with man's law and more about divine law. Themis embodied and taught mankind about divine law, natural order, proper conduct and good governance. She sat on the throne at Olympus and gave counsel to Zeus.
In Themis we can see all the typical characteristics of the Libran essence: natural law through divine awareness, social grace and courtesy, awareness of the desires and points of view of others and not the self alone in seeking what's best through consensus rather than domination. Even the desire for peacemaking and balance is represented in her as she was not wrathful or petty as many gods and goddesses typically were portrayed. She presided over what is naturally lawful and is the embodiment of justice at its highest intent, which is peaceful. This idea of justice is not intended to give visions of vigilante vengeance. That was the job of Nemesis, who was the Greek personification of divine retribution and stepped in when divine law was not heeded. The name Nemesis is taken from the Greek word that means 'to give what is due,' which was inherently neither good nor bad, but is direct consequence from one's actions. However, it gradually became more of a negative connotation, as is evident by what we think of when we hear phrases like 'getting what they deserve.'
The constellation of Libra, the image of the scales, is actually held by Virgo. One of the goddess links to the personification of Virgo is the goddess Astraea, who is the daughter of Themis. It is she who is said to hold the scales in the sky and flew to heaven when the laws of man became so corrupted that she withdrew.