Natasha Yar was born on the failed colony world of Turkana IV.1 Her childhood was typical of that world; she spent her life scavenging for food for the family, attempting to avoid the rape gangs which roamed the colony. Her parents where killed when she was five, and Tasha was subsequently raised by her sister. She refused to accept the conditions in which she found herself, and at the age of fifteen she managed to convince a passing trader to take her away from the colony.2
She ended up on a Federation planet, where she was assigned refugee status; after two years she joined Starfleet Academy, graduating in 2359.
Yar performed exceptionally both in the Academy and on active duty. By 2364 she had been assigned as Chief Tactical Officer of the Enterprise-D3 at the request of Captain Picard, who had been impressed when he saw her negotiating a minefield to save the lives of some trapped personnel.2 An expert at many types of fighting, Yar was favoured in the ship's pool during martial arts competitions.4 She secured a vital vaccine for the Federation by defeating Yareena, wife of Ligonian leader Lutan, in single combat.5 Yar made several good friends on board the ship, including Geordi LaForge. Whilst under the influence of a form of the Psi-2000 virus she even became intimate with Data, much to her subsequent embarrasment!1 She also expressed some romantic interest in Captain Picard, though his role as Captain precluded any involvement.6 While on an away mission to rescue the crew of a shuttle crashed on Vagra II, Enterprise crewmen encountered an entity which called itself Armus. Armus, who claimed to be an embodiment of pure evil, prevented the away team from reaching the shuttle. When Yar tried to walk around Armus he killed her with an energy discharge.
Natasha left a message for her shipmates in which she thanked them for being a part of her life and told them how much she had enjoyed being a part of the Enterprise crew.4
In 2367 a Romulan operative, Sela, claimed to be Tasha Yar's daughter - an absurd claim on the face of it as Sela was approximately the same age that Yar would have been had she lived. Guinan told Captain Picard that an temporal anomaly involving the Enterprise-C had led to a Tasha Yar from an alternate timeline being captured by the Romulans some decades in the past; this Yar had agreed to become the consort of a Romulan in return for the lives of the rest of the Enterprise-C's crew. Yar was killed some years later whilst trying to escape with her daughter.7