(covers information from several alternate timelines)
Lieutenant Natasha Yar, better known as Tasha, was a Human Starfleet officer born on Turkana IV, and former security chief on the USS Enterprise-D. Tasha Yar was killed not even a year into the Enterprise's mission. She was fondly remembered by the Enterprise crew, and an alternate version of Tasha indirectly played a very important role in Romulan politics. (TNG: "The Naked Now", "Legacy", "Skin of Evil", "The Bonding", "Yesterday's Enterprise", "Redemption II", "Unification II")
Tasha was born in 2337 on the failed Federation colony world of Turkana IV. Her sister, Ishara, was born five years later. Both of their parents were killed shortly after Ishara's birth, after which they were looked after for a few months by "some people" who later disappeared, leaving Tasha to care for herself and her sister. (TNG: "Legacy") Tasha had to avoid rape gangs and terrible violence just to scavenge for the bare necessities of life, such as food. One of the few bright spots in her life was finding a cat, which she attempted to protect while being chased by a rape gang. (TNG: "Where No One Has Gone Before") Narcotic use was also commonplace. Tasha apparently resorted to drugs as an escape at some point, but later remembered that they were of more harm to her than good. (TNG: "Symbiosis")
Although Ishara decided to remain on the planet and eventually joined the Coalition, Tasha managed to find a way off Turkana IV in 2352 by the age of fifteen. Ishara and Tasha never saw one another again. (TNG: "Encounter at Farpoint", "Legacy")
Academy and early assignments
Tasha began to attend Starfleet Academy soon after her escape and credited Starfleet with saving her from her previous life. (TNG: "Encounter at Farpoint", "Legacy") She joined Security because of the lawless environment in which she grew up. (TNG: "Code of Honor")
In 2363, while conducting a rescue mission, Yar rescued a colonist after traversing a Carnelian minefield. Captain Jean-Luc Picard's ship at the time was also present. Picard was so impressed with her bravery that he recruited Yar for duty on the Enterprise, as Yar's current commanding officer owed him a favor. (TNG: "Legacy")
Yar piloted Picard to the Enterprise-D in the shuttlecraft Galileo for his first visit to the ship. She set out to Farpoint Station from Earth Station McKinley with most of the crew. (TNG: "All Good Things...") En route, the Enterprise was intercepted and detained by the Q entity. Tasha wanted to fight him, but Picard refused her suggestion because of the tremendous power of the Q. While the senior staff was taken to the 21st century courtroom and put on trial by Q, Yar could no longer resist the urge to tell Q he was wrong for accusing humanity of "savage, childlike behavior." She was placed into a sort of deep freeze by Q as punishment, but was later revived.
Later, Yar took part in several away teams which investigated Farpoint Station and the living station's mate, which returned to seek vengeance against the Bandi for imprisoning the other creature. (TNG: "Encounter at Farpoint")
While the Enterprise was negotiating at the world of Ligon II for vaccine needed on Styris IV, the Ligonian leader Lutan became impressed with Tasha's martial arts skills and her physical beauty. As a show of defiance and boldness in line with the Ligon Code of Honor, he kidnapped her and brought her to his planet. Picard needed to negotiate both for her safe return and for the vaccine. However, Lutan was determined to have Yar as his First One, the ceremonial title of his wife. The current First One, Yareena, challenged Lutan's decision, requiring Yar to participate in a fight to the death with Yareena. In order to satisfy the needs of the culture and return to the Enterprise, Tasha fought and killed Yareena. Fortunately, samples of the poison used on Yar's weapon was returned to the Enterprise by Data, allowing Doctor Beverly Crusher to develop an antidote and revive Yareena once they were brought to the Enterprise. Yareena stripped Lutan of his title and offered him to Tasha, but she refused, stating that there would be "complications". (TNG: "Code of Honor")
When the Enterprise was transported beyond the known universe by the Traveler, to a place where matter and thought were not distinct, Yar hallucinated that she had returned to Turkana IV and was being chased by the rape gangs. (TNG: "Where No One Has Gone Before")
Because of the matriarchal nature of the society on Angel I, Yar took informal command of the away team while Commander William T. Riker negotiated for the release of survivors from the freighter Odin. When Riker put on one of the sexualized outfits worn by men on the planet, she and Deanna had a good laugh at the first officer's expense. (TNG: "Angel One")
Tasha was killed in late 2364 on the planet Vagra II. She was part of an away team sent to rescue Deanna Troi and Ben Prieto, who had crashed there aboard a shuttle. Their rescue was impeded by a lifeform known as Armus. When Yar tried to walk around Armus to get to the shuttle crew, Armus attacked and killed her without warning, simply as a display of his power. Dr. Crusher tried to revive her but she was too badly injured, as the life had been "drained" from her. The officially recorded cause of death was heavy synaptic damage.
A service was held for Tasha in the holodeck following the rescue of the crew from the surface, where a holographic message from Tasha was played. Tasha always believed her death would happen quickly and while on duty, and that was the way she wanted it. (TNG: "Skin of Evil")
Yar was an expert in aikido, a form of martial arts, and regularly used several holodeck training programs. (TNG: "Code of Honor") She was also a parrises squares player. (TNG: "11001001") At the time of her death, Yar was scheduled to participate in a martial arts competition with science officer Swenson and Lieutenant Minnerly, which was to take place three days later. She was favored in the ship's pool. (TNG: "Skin of Evil")
Tasha barely remembered her father and called herself an orphan like Worf. During her recorded funeral speech on the holodeck in 2364, she addressed Jean-Luc Picard and told him that he would be the person in the universe she would call a father figure. (TNG: "Skin of Evil")
Yar saw Captain Picard as an informal father figure. She found support in Picard when she was confined to a "penalty box" as part of a deadly game run by Q during the Enterprise's second encounter. She had been placed there as punishment for challenging Q, and would have been consigned to oblivion if another officer had been sent to the penalty box. Tasha was frustrated and upset by the situation and began to cry. Picard said she was permitted the feelings and that they were in no way a show of weakness. (TNG: "Hide and Q")
Tasha was often uncomfortable in expressing her femininity, and for that reason sometimes sought the help of Deanna Troi. While under the influence of a polywater intoxication in 2364, Yar entered Troi's quarters and tried on several articles of her clothing. (TNG: "The Naked Now")
Yar was also very good friends with Worf, who, as a Klingon warrior, greatly admired her physical combat skills. Together, they took part in a parrises squares tournament against the Starbase 74 maintenance crew in 2364. (TNG: "11001001") Worf also placed a wager on Yar's victory in the martial arts competition which she was to have participated before her death. Yar was touched by this gesture.
In the holographic message she prepared in the event of her death, Yar spent a brief moment addressing each of her friends. She called Will Riker "the best," and was grateful for his trust, encouragement, and humor. She said Deanna proved to her that she could be feminine without losing anything. Yar saw a kindred spirit in Worf, as they were both warriors and orphans who found a place in this family. Tasha admired Beverly Crusher's fierce and unstoppable devotion, and from her learned to strive for excellence no matter what the personal cost. She regretted that she would be unable to see Wesley Crusher grow to become an exceptional young man. Yar was thankful for Geordi La Forge's friendship and support in times of despair. She assured Data that his way of viewing the universe from the perspective of a child made him the most human of the entire group. Tasha said she considered Picard to be like a father, but she was unable to tell for sure because she had never had a father. However, she felt he had the "heart of an explorer and the soul of a poet" and that if she could pick one person to be like, it would be him. She concluded by saying that death was not a goodbye since she would always live on in their memories. After the service, Data was confused, thinking he had missed the point of her funeral because his thoughts were not for Yar, but for himself and how her presence would be missed. However, Picard assured him that he understood perfectly. (TNG: "Skin of Evil")
The pain of Tasha's death was recalled several times by the Enterprise crew, such as when Marla Aster died (TNG: "The Bonding") and when Data was believed killed in a shuttle accident in late 2366. (TNG: "The Most Toys") Riker used Tasha's death as an example of how he felt the ritual Klingon suicide was a cowardly escape when Worf considered it following a paralysis in 2368. (TNG: "Ethics")
When the Enterprise went to Turkana IV in 2367 to rescue the crew of the Arcos, Ishara helped the crew rescue the survivors from the Turkana IV Alliance forces. She expressed a desire to leave and join Starfleet like her sister, which charmed the crew into trusting her and perhaps seeing more of Tasha in Ishara. Her interest in leaving Turkana was later determined to be mostly a deception in order to use the rescue mission to cripple the Alliance. (TNG: "Legacy")
Yar was at least slightly attracted to Data and had sex with him while under the influence of polywater intoxication. She later told him that the incident "never happened". (TNG: "The Naked Now") Data still felt a special connection to Tasha and later mentioned that he and Tasha were intimate. He kept a holographic image of Tasha to remember her. When Data's rights as a sentient being were called into question, his romantic encounter with Tasha was a strong influence for Judge Phillipa Louvois to rule that Data was in fact a sentient lifeform, as Data admitted that she was 'special' to him even when he had no emotions to influence his thoughts on personal relationships. (TNG: "The Measure Of A Man") La Forge and Wesley Crusher found the holoimage when they visited Data's quarters after his apparent death in 2366. (TNG: "The Most Toys")
Yar also had random romantic encounters with several Enterprise crewmembers while affected by the polywater intoxication. Geordi La Forge originally passed on the intoxication to Tasha, and he expressed lustful feelings towards her. (TNG: "The Naked Now") La Forge also told Yar that she was more beautiful than he imagined once he was briefly granted normal sight by Commander Riker, bestowed with the powers of the Q Continuum. (TNG: "Hide and Q")
Alternate realities and timelines
Temporal rift timeline
In an alternate timeline created by the USS Enterprise-C's transit from 2344 to 2366 through a temporal rift, Tasha had not been killed at Vagra II, and continued to serve as tactical officer aboard the Enterprise-D during a war between the Federation and the Klingon Empire. Tasha had joined the Enterprise-D crew immediately upon graduating from Starfleet Academy in 2362.
In 2366, the Enterprise-D encountered the Enterprise-C as it emerged from the temporal rift, after the Enterprise-C had nearly been destroyed in a Romulan attack on the Klingon outpost at Narendra III. During the course of making repairs to the Enterprise-C, Tasha became close to a crewmember from that ship, Lieutenant Richard Castillo, and the two of them developed romantic feelings for one another. She later became aware, through Guinan, that in the other timeline she had died a meaningless death. When the Enterprise-C's captain, Rachel Garrett, was killed in a Klingon attack, Tasha requested permission from Captain Picard to transfer to the Enterprise-C and accompany it back through the rift in an attempt to restore the timeline, explaining that she wanted her death to count for something. Captain Picard granted her request. Although Castillo, who had assumed command of the Enterprise-C, was initially reluctant to accept Tasha on an apparent suicide mission, he relented and assigned her to the tactical position. Entering the rift just as three Klingon Birds-of-Prey began attacking both Enterprises, the Enterprise-C successfully returned to its own time, where it played an instrumental role in guaranteeing peace between the Federation and the Klingon Empire, restoring the flow of history. (TNG: "Yesterday's Enterprise")
While the Enterprise-C was destroyed, several crewmembers survived and were taken prisoner by the Romulans, Tasha among them. According to Sela, after being interrogated, all of the survivors were to be executed, but a Romulan general became enamored of Tasha and offered to spare the lives of the prisoners if she became his consort, a condition to which Tasha agreed. One year later she gave birth to a daughter, Sela. When Sela was four years old, Tasha took her and attempted to escape, but sensing that her mother was taking her away from her home and her father, Sela cried out, and Tasha was discovered and subsequently executed. These events were completely unknown to Starfleet until 2368, when the Enterprise-D encountered Sela, by then a commander in the Romulan military, during her attempt to covertly support the Duras sisters in taking control of the Klingon Empire. (TNG: "Redemption II")
Anti-time past timeline
Another alternate version of Yar was seen by Captain Picard in the anti-time past. This timeline diverged during the shuttle trip to the Enterprise back in 2364. Picard was somewhat disoriented during his initial shifts from the other two time periods, and was distracted at seeing Yar again. He also mistakenly gave orders about ship security to Worf. Yar went along with Picard's unusual orders to proceed to Farpoint Station in lieu of investigating a temporal anomaly in the Romulan Neutral Zone, and again when Picard decided to go to the anomaly after all. When Picard made the decision to enter the anomaly and create a static warp shell, Yar, along with the rest of the bridge crew, momentarily hesitated. However, Picard was able to convince the crew of the importance of the task and Tasha struggled to keep the antimatter containment field maintained until the past Enterprise was destroyed. (TNG: "All Good Things...")
- "Encounter at Farpoint"
- "The Naked Now"
- "Code of Honor"
- "Where No One Has Gone Before"
- "The Last Outpost"
- "Lonely Among Us"
- "The Battle"
- "Hide and Q "
- "Too Short a Season"
- "The Big Goodbye"
- "Angel One"
- "Home Soil"
- "When The Bough Breaks"
- "Coming of Age"
- "Heart of Glory"
- "The Arsenal of Freedom"
- "Skin of Evil"
- "The Schizoid Man" (image)
- "The Measure Of A Man" (hologram)
- "Shades of Gray" (archive footage)
- "Yesterday's Enterprise"
- "The Most Toys" (hologram)
- "All Good Things..."
Tasha Yar was played by Denise Crosby during the first season of Star Trek: The Next Generation. Crosby was a part of the Next Generation regular cast from TNG: "Encounter at Farpoint" to "Skin of Evil", although she was listed in the main credits for the remainder of the first season. Also, "Symbiosis" was filmed after "Skin of Evil", meaning that episode was technically Crosby's final as a regular cast member. In a scene near the end of "Symbiosis", Crosby can be seen waving at the camera, waving goodbye to all of her fans. The wave is only visible for a few seconds (40:26 - 40:30), as Captain Picard and Dr. Crusher are exiting the cargo bay, but can easily be seen on DVD with frame-by-frame advancement.
Yar was the first regular character to depart a Star Trek series while in production and also the first to be killed off without being resurrected. Crosby returned for guest spots as Yar in "Yesterday's Enterprise" and "All Good Things...", and can be seen in holographic form in "The Measure Of A Man" and "The Most Toys". The character also appears in flashback stock footage during treatment Riker receives in "Shades of Gray", and during a personality test Data undergoes in "The Schizoid Man". Due to an editing gaffe, Crosby's shoulder and left arm also appear in the episode "We'll Always Have Paris", set after her character's death in "Skin of Evil".
The character of Yar was indirectly inspired by Jenette Goldstein's space marine character Vasquez from the motion picture Aliens. (Star Trek: The Next Generation Companion) Gene Roddenberry and Robert Justman watched Aliens during the early stages of preparation for the series, and Roddenberry expressed his wish to create a character named "Macha" based on Vasquez.  Recalled David Gerrold, "After Aliens, Gene would say about Jenette Goldstein, 'That woman created a whole new style of feminine beauty. We should have something like that in Star Trek.' So we started off with a character named Macha Hernandez, who eventually became Tasha Yar. That sparked an idea for Gene." Justman was also inspired by Goldstein. He later remembered thinking, "If we could get her, she could be a member of the Enterprise's onboard Marine or MP contingent. This would enable her to serve in a military capacity within our landing parties. Her feistiness, coupled with her earthy physicality, could create interesting opportunities for drama." (The Fifty-Year Mission: The Next 25 Years, p. 57)
"LT. Macha Hernandez – 26 year old woman of unspecified Latin descent who serves as the starship's security chief. She is described as having a new quality of conditioned-body-beauty, a fire in her eyes and muscularly well developed and very female body, but keeping in mind that much of her strength comes from attitude. Macha has an almost obsessive devotion to protecting the ship and its crew and treats Capt. Picard and Number One as if they were saints."
"The starship security chief, Tasha, who performs that same function both aboard ship and on away missions. Born at a 'failed' Earth colony of renegades and other violent undesirables, she escaped to Earth in her teens and discovered Starfleet, which she still 'worships' today as the complete opposite of all the ugliness she once knew."
Among the performers who were considered for the role of Tasha Yar were Lianne Langland, Julia Nickson, Rosalind Chao, Leah Ayers, and Bunty Bailey.  Nickson and Chao were well liked for the part. (The Fifty-Year Mission: The Next 25 Years, p. 97) By 13 April 1987, Chao seemed to be a favorite candidate. 
Originally, Marina Sirtis auditioned for this role, while Denise Crosby read for Deanna Troi. Gene Roddenberry decided that each would be better as the other's character, and Macha's description was altered to reflect Crosby's blonde looks. First, the character's name was changed to "Tanya", then to "Tasha Yar", based on a Ukrainian ravine named Babi Yar, where massacres took place during a Nazi Germany campaign against the Soviet Union in World War II. (Star Trek: The Next Generation Companion, p. 15)
Denise Crosby once commented, "They originally envisioned Tasha as more butch [...] What I liked about Tasha is she's strong physically and direct and is comfortable with who she is. I envisioned Tasha as what I brought to it. I sort of like the quality that she could be attractive and sexy and still be able to kick the shit out of anyone." The actress also reckoned that her experience of growing up as the granddaughter of famous Hollywood celebrity Bing Crosby, since that "wasn't exactly normal or typical," helped her "understand Tasha's imbalance and insecurities." (The Fifty-Year Mission: The Next 25 Years, pp. 97-98)
Yar is the only main character besides Troi to wear a "skant" version of the Starfleet uniform, which she does in the last scene of "Encounter at Farpoint"; Yar is behind the tactical console, but the skant is just visible.
According to the Star Trek: The Next Generation First Year Sourcebook, Tasha Yar was born on Hokma V.
The alternate-timeline Tasha Yar appears (voiced again by Denise Crosby) in the Star Trek Online mission "Temporal Ambassador". The mission reveals that the Enterprise-D's battle with the Klingons in "Yesterday's Enterprise" caused the Enterprise-C to emerge from the temporal rift in the Azure Nebula in 2409, rather than Narendra III in 2344. The alternate timeline remains, and the Federation has fallen to the Klingon Empire, which in turn has fallen to the Dominion. The Enterprise and her crew are captured by the Tholian Assembly and held aboard a base in the Azure Nebula, where the player must help them escape and reach the temporal rift so they can return to 2344.
She later returns, though posthumously, in "Survivor". There, it's revealed that the alternate-timeline Tasha Yar was never actually killed, instead left on a Tal Shiar prison colony along with the other Enterprise-C crewmembers. Through various datapads left by Yar, the player, along with Sela and Agent Daniels, learns that the crew fended for themselves after the Tal Shiar abandoned the colony following the destruction of Romulus and Remus by the Hobus Supernova. The crew would die one by one, either killed by the creatures on the planet or by temporal anomalies caused by the existence of an alternate Admiral T'Nae. Yar would be the last to die, wishing for the crew to be remembered somehow. T'Nae buried her and was eventually rescued and reintegrated with her prime counterpart, while Sela agreed to be put under arrest on the condition Starfleet help her learn more about Tasha.