Bartholomew "Bart" JoJo Simpson is a fictional main character in the animated television series The Simpsons and part of the eponymous family. He is voiced by actress Nancy Cartwright and first appeared on television in The Tracey Ullman Show short "Good Night" on April 19, 1987. Bart was created and designed by cartoonist Matt Groening while he was waiting in the lobby of James L. Brooks' office. Groening had been called to pitch a series of shorts based on Life in Hell but instead decided to create a new set of characters. While the rest of the characters were named after Groening's family members, Bart's name was an anagram of the word brat. After appearing on The Tracey Ullman Show for three years, the Simpson family received their own series on Fox, which debuted December 17, 1989.

At ten years of age, Bart is the eldest child and only son of Homer and Marge, and the brother of Lisa and Maggie. Bart's most prominent character traits are his mischievousness, rebelliousness and disrespect for authority. He has appeared in other media relating to The Simpsons—including video games, The Simpsons Movie, The Simpsons Ride, commercials, and comic books—and inspired an entire line of merchandise.

In casting, Nancy Cartwright originally planned to audition for the role of Lisa, while Yeardley Smith tried out for Bart. Smith's voice was too high for a boy, so she was given the role of Lisa. Cartwright found that Lisa was not interesting at the time, so instead auditioned for Bart, which she thought was a better role. Hallmarks of the character include his chalkboard gags in the opening sequence; his prank calls to Moe the bartender; and his catchphrases "Eat my shorts", "¡Ay, caramba!", and "Don't have a cow, man!"