The Enterprise-D's first chief of security.
Tasha Yar is the security chief of the Enterprise-D in the first season of The Next Generation, played by Denise Crosby. Raised on the failed colony of Turkana IV, she survived a violent childhood before escaping and joining Starfleet, and she brings a fierce toughness to the role.
In The Naked Now she and Data have a brief intimate encounter while under the influence of an intoxicating disease, and the bond between them lingers. She is killed in Skin of Evil by Armus, a malevolent creature on Vagra II, and the crew gather for a holographic farewell message she recorded.
She returns in Yesterday's Enterprise, set in an alternate timeline in which she is still alive. Learning that she died a meaningless death in the true history, she volunteers to go back in time with the Enterprise-C, a choice that leads to her capture by the Romulans and the birth of her daughter Sela. She appears once more in the series finale, All Good Things.