Tiris Jast was a female Bolian in the 24th century. In 2376 she held the rank of Commander in Starfleet and was assigned command of the starship USS Defiant late in the year 2375.
Jast arrived at the station during the N-Vector viroid incident, and got off on the wrong foot with station commander, Colonel Kira Nerys, but the two eventually earned each other's respect. Jast was assigned by Starfleet Internal Affairs to investigate Miles O'Brien.
Jast was in command of the Defiant and patrolling the Bajor sector when the ship was temporarily caught in a warp dead zone.
Jast was killed in action onboard the Defiant in April of 2376 when the ship was attacked by a trio of rogue Jem'Hadar vessels.