Bartholomew "Barry" Allen is a forensic scientist for the Central City Police Department. After his lab was struck by lightning and he was doused with chemicals, he gains the ability to move at superhuman speeds. Originally intending on using his abilities to bring his brother's murderer to justice, he later becomes the hero of Central City known as The Flash.
While celebrating his brother, Jay Allen's birthday with the rest of his family, Barry was summoned to the crime scene at West Ridge after the aftermath of recent bombings by the Dark Riders. Later, Barry and Julio Mendez both work in the lab, examining soil samples they took from the crime scene. Eventually Julio begins to fall asleep, and is sent home by Barry. While he's working, lightning strikes Barry's lab, dousing him with chemicals from a nearby shelf. Barry is then found by Julio on the floor, and taken to the hospital. He leaves the hospital the next morning as all the tests the doctor ran tested negative, going to Hudson Diner with Iris West. After the two get into an argument over marriage, Barry leaves back to the lab, and while there receives a call from Dr. Lawrence, who informs him that there was cell damage from Barry's accident, and not knowing what to make of it, sent the results to Star Labs.
Barry angrily informs Julio of this, and refuses to have anything to do with Star Labs, as one of their employees died last year in one of their experiments.
At one point, Mar Novu, as known as the Monitor, traveled to Earth-90 to test it. It was ultimately destroyed, leaving Barry as its sole survivor. He traveled to Earth One to warn Green Arrow, the Earth-1 Flash, and Supergirl of the Monitor's threat to the multiverse. He along with the other heroes confronted the Monitor, to whom he firmly stated that he would not do to this earth what he did to his. The Flash then charged to attack before the Monitor made hi vanish, leaving his fate unknown.
- Barry Allen debuted in Showcase #4 (October 1956) after his lab is struck with lighting that mixes with chemicals that spill onto him, he gains the ability of super speed becoming the hero commonly known as the Flash. He later dies in Crisis on Infinite Earths but is resurrected in Final Crisis.
- The Flash marked Barry Allen's second live action appearance; previously appearing in Legends of the Superheroes and later appearing in Smallville, and the 2014 television adaption of The Flash.
- John Wesley Shipp who portrayed Barry Allen/The Flash also portrayed Henry Allen and Jay Garrick in the 2014 television adaption of The Flash.