Colonel Shaun Geoffrey Christopher was a male Human military service member. He was born after 1969 to US Force Captain John Christopher and his wife. Shaun had two older sisters. In the early 21st century, he was the commander of the first successful mission to Saturn. He was accompanied on this mission by the astronauts Fontana and O'Herlihy.
In 1969, the USS Enterprise, which had accidentally traveled back in time from the year 2267, took aboard Shaun's father Captain John Christopher when he attempted to intercept the Enterprise with his F-104 Starfighter. Initially believing that returning Christopher to Earth would be impossible due to the fact that he might inadvertently change history with his new-found knowledge of the future, Lieutenant Commander Spock eventually realized that he had to be returned, or Shaun Geoffrey Christopher would never be born and the Saturn mission would never take place. (TOS: "Tomorrow is Yesterday"; ENT: "First Flight")
According to Star Trek Encyclopedia (3rd ed., pp. 75-76), Shaun Geoffrey Christopher was named after writer John D.F. Black's three sons: Shaun, Geoffrey, and Christopher. According to Star Trek Chronology, the mission to Saturn took place in 2009. According to the Star Trek Spaceflight Chronology, the mission took place in 2020.
In the short story "Assignment: One" of Strange New Worlds 8, Gary Seven was assigned to prevent Christopher from boarding one of the airplanes that was involved in the September 11th terrorist attack.
The novel The Rings of Time detailed the Saturn mission that Christopher commanded in 2020. During the mission, he and Captain Kirk switch bodies due to the effects of an alien probe, with Kirk saving Christopher's ship from sabotage by the contemporary terrorist organization the Human Extinction League (β), while Christopher uses knowledge gained from the probe to prevent the collapse of a gas planet's rings by triggering an ancient 'reboot'. The Enterprise subsequently travels back to 2020 via the Slingshot effect so that Spock can return Kirk and Christopher to each others' bodies via a mind meld.
Commander Shaun Christopher was the main character of the Star Trek: Live stage show produced by Mad Science Productions and performed at various locations from 2010–2011, including Kennedy Space Center Visitor Complex.
The novelization of the episode "Relics" gave the name of the shuttle "loaned" to Montgomery Scott as the Christopher, named for Shaun Geoffrey Christopher; however in the episode, the name Goddard was legible on the hull. Allegiance in Exile also gives this as the name of a shuttle on Kirk's Enterprise, though it is unclear whether it was named after him or not.