Tasha Yar

Natasha "Tasha" Yar was a human Starfleet officer in the late 24th century, and is best known for serving as the Chief Security Officer of the USS Enterprise-D from its maiden voyage up until her untimely death at the hands of the Armus creature several months later. Fellow crewman Lieutenant Commander Data was fond of Tasha, experiencing his first incidence of sexual intercourse with her, and after her death kept a small holographic ornament of her on the desk of his personal quarters. In 2412, an alternate version of Yar was discovered serving on a penal colony ruled by Tholians. She was the instigator of an underground movement and assisted Mirra Boleros and Admiral T'Nae in escaping aboard the captured USS Enterprise-C.