While Brad Pitt can still be correctly referred to as Brad Pitt, technically Brad isn't his first name. The actor's full name is William Bradley Pitt, after his father, William Alvin Pitt. So, even the name Brad is just a shortened version of his middle name. 

After leaving Missouri to pursue a career in acting, Pitt chose to drop his first name and shorten the middle name, most likely to give it the snazzy feel of an easily pronounceable name, per Glamour. On the circumstances leading to his Missouri exit, Pitt explained that he was due to graduate school, but just could not wait anymore to start pursuing his movie career. He upped and left before obtaining a degree. "I'd always lamented that there wasn't an avenue for film in Southern Missouri, and it just occurred to me that I could go to it, and I literally loaded up the car. I didn't graduate," Pitt told Leonard Maltin at the Santa Barbara International Film Festival in 2020, per Collider.

Brad Pitt is not the only actor to have modified or completely changed names in order to establish themselves in Hollywood. Jamie Foxx is popular by that name now but one wonders if that would be the case if he had stuck with his real name, Eric Marlon Bishop, per Insider. Even the ever-iconic Marilyn Monroe switched things up. Her original name was Norma Jeane Mortenson!