Stefan Bartok was a Human Starfleet officer serving in the 24th century.
He was present at the Battle of Wolf 359 aboard the USS Yamaguchi as Chief of Security. As a member of the ship's Security Department, he engaged Borg drones while leading personnel to the escape pods.
He later became a weapons specialists aboard Starbase 324, researching ways to combat the Borg.
In 2372 the USS Lionheart served as a mission platform for him and a team of specialists to search Minos for weapons technology. ("Return to the Arsenal")
His team spent five months exploring the planet, supported by the USS Mandela. Afterward, they and their work moved to Starbase 324.
In 2374 he was promoted to Captain and placed in command of the newly commissioned USS Angistri. ("Reinforcements")