- See Finnegan for other articles with titles that contain, either by relationship or by coincidence, this character's surname.
- This page details Sean Finnegan in the primary universe; for the Sean Finnegan in the mirror universe see Sean Finnegan (mirror).
- This page details Sean Finnegan in the primary universe; for the Sean Finnegan in the Kelvin timeline created by Nero's temporal incursion see Jake Finnegan.
In late August 2250, Finnegan supervised a group of cadets during training aboard the USS Enterprise, then undergoing a refit. Also aboard were Kirk and Spock, who were posing as cadets. Finnegan supported Kirk and Spock when they pointed out inconsistencies in a second-year cadet's story. In so doing, he played a key role in the prevention of the theft of dilithium from the Enterprise. (TOS episode: "Shore Leave"; TOS novel: Academy: Collision Course)
During his final year at the academy, he received a promotion to ensign. He took particular pleasure in tormenting then-Cadet Kirk that year. He graduated from the Academy in 2251, and was assigned to a starship patrolling the Romulan Neutral Zone. (TOS novel: Captain's Peril; TOS - My Brother's Keeper novel: Republic)
As a commander in Federation Security, Finnegan returned to tease Kirk in late 2286, after an attempt on the latter's life aboard the starship Enterprise-A. Finnegan surmised the secret behind the attempt, but was attacked and rendered unconscious before he could inform anyone that Garth of Izar, once again mad, was bent on Kirk's murder, disguised as various unwitting accomplices. (TOS - Who Killed Captain Kirk? comics: "Old Loyalties", "Finnegan's Wake!")
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