Admiral Cartwright was a human Starfleet officer in the latter half of the 23rd century. As an Admiral he served as Commander-In-Chief, Starfleet Command. In addition he was the Starfleet liaison to the Diplomatic Corps.
By 2268 Cartwright was the Rear Admiral who ordered Captain Kirk and Mr. Spock to retrieve a Romulan cloaking device. Even then Kirk was suspicious of the Admiral having a secret agenda.
In 2286 Cartwright led Starfleet's response when an alien probe looking for humpback whales began causing severe climatic disruption on Earth.
After the destruction of Praxis in 2293, the Klingon Empire sued for peace. Cartwright was a vocal opponent of the peace process, wanting to attack the Klingons, defeat them, and dictate terms. However Starfleet and the Federation Council did not accept his recommendations and supported the peace process.
Cartwright then got in touch with other members of Starfleet who felt as he did - including young Lieutenant Valeris, along with people in the Klingon and Romulan Empires who stood to lose if hostilities ended. Because Kirk had voiced support for some of Cartwright's positions, Cartwright and his co-conspirators used Kirk as a scapegoat when they assassinated the Chancellor of the Klingon Empire. They framed Captain Kirk and Doctor McCoy for killing Gorkon, and planned to assassinate the Federation President - an act they intended to blame on the Klingon Empire. Ironically, Kirk's battle prowess had the conspirators ask the Federation President for permission to stage a rescue mission, reasoning they would need Kirk once the war began. But the President rejected this as well.
However Kirk and McCoy were able to escape from Rura Penthe. With help from Captain Sulu of the USS Excelsior, the crew of the Enterprise arrived in time to the renewed peace talks to prevent the assassination. Cartwright attempted to flee but was arrested by Sulu and an Excelsior security team.
Cartwright was convicted for his role in the conspiracy and sent to prison. He died in prison in 2298 of apparent natural causes. Some in Starfleet thought that one of his many enemies had arranged for him to be killed in a way that appeared to be natural. As a result of his death Valeris as the only known survivor of the conspiracy.
- Cartwright was portrayed by Brock Peters, who was best known for playing Tom Robinson in To Kill a Mockingbird as well as Benjamin Sisko's father Joseph in Star Trek: Deep Space Nine.
- The script gave Cartwright's first name as Donald. Other licensed media gave Cartwright's first name as Lance.