Tia Organa was a Human female, belonging to the Organa family from Alderaan. She was the sister of Bail, Celly, and Rouge Organa, and also the adoptive aunt to Leia Organa.
As a member of House Organa, Tia Organa spent her childhood on Alderaan alongside her siblings. Some years prior to the onset of the Clone Wars, Organa was scheduled to be wed to a nobleman from House Vandron. However, Organa had entered into a clandestine relationship with Halagad Ventor, a friend and associate of her brother Prestor Organa. During this affair, Organa accompanied her brother and Ventor on a hunting trip for manka cat at the Okonomo Retreat, where the geneticist Zeta Magnus infiltrated the Retreat building and infected all of the revelers, including Ventor's parents, with a hive virus. The virus drove the partygoers insane, and they began devouring each other in a cannibalistic frenzy before they were ultimately consumed by Magnus. Upon hearing about the tragedy, Ventor deserted Organa, leaving her pregnant and alone. The scandal caused a political uproar in Aldera City, resulting in the dissolution of the alliance between House Organa and House Vandron. She later gave birth to a son, whom she named Nial Organa.
Organa owned several pittins that she pampered, treating them as if they were her own offspring. These included All-Terrain Attack Vehicle, Taffy, Winkie, and Fluffy.
Tia Organa was present on Alderaan in 0 BBY when Grand Moff Wilhuff Tarkin gave the order for the destruction of the planet. When the Death Star targeted Alderaan and annihilated it in a matter of seconds, Organa died along with her son and all other Alderaanians on the planet.
Tía is Spanish for aunt in the real world.