Bart Allen is a speedster, the original character known as Impulse, the second Kid Flash, and the fourth hero known as The Flash. Originally born in the 30th Century as a descendant of the Allen Family, he traveled back to our time and became a member of the Flash Family. His grandfather is Barry Allen, and his mentors have included Wally West and Jay Garrick, along with Max Mercury. Originally given the codename Impulse for his impulsiveness, he became Kid Flash after learning greater self-control, and eventually The Flash when he grew up further. Bart was killed by the Rogues during Full Throttle, but resurrected as Kid Flash again during Final Crisis, he has been working alongside the other three Flashes since the events of The Flash: Rebirth. He is a founding member of Young Justice and a member of the Teen Titans and Legion of Super-Heroes.
In the New 52 reboot, a new character appears using the same name as the original Bart Allen, and is portrayed as a teenage terrorist of the future whose real name is revealed as Bar Torr, his powers are not come from Speed Force. The original Bart Allen makes his return in Flash War as Impulse.