Captain Sulu was a Starfleet officer.

In 2344, he was among the officers patrolling the Cardassian border that became acquainted with a young Chakotay. When Chakotay requested a sponsorship to get into Starfleet Academy, he told the captain that Kolopak approved, then kept Sulu as far away from Kolopak as he could so his lie wouldn't be found out. Chakotay admitted this to Kolopak when he informed his father of his intentions to leave the tribe and attend the Academy. (VOY: "Tattoo")

This character was only mentioned in dialogue. in this episode.
Chakotay used the male pronoun "he" when referring to Captain Sulu. The Star Trek Encyclopedia (2nd ed., p. 70) suggests that this was probably intended to be a reference to Captain Hikaru Sulu, who would have been 107 in 2344. Given Doctor McCoy's tour of the USS Enterprise-D as an admiral at age 137 (TNG: "Encounter at Farpoint"), this would not be as implausible as it might seem. Further complicating the issue, the non-canon book Pathways states this is Hiromi Sulu, the grandson of Hikaru Sulu and son of Demora Sulu.
The non-canon anthology Tales from the Captain's Table states that it was in fact Sulu's daughter Captain Demora Sulu who sponsored him (She would have been 76). The story also suggests an explanation for why Chakotay specifically referred to the Captain Sulu who sponsored him as "he" in "Tattoo".
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