Bartholomew Jojo "Bart" Simpson is a fictional character in the American animated television series The Simpsons and part of the Simpson family. He is voiced by Nancy Cartwright and first appeared on television in The Tracey Ullman Show short "Good Night" on April 19, 1987. Cartoonist Matt Groening created and designed Bart while waiting in the lobby of James L. Brooks' office. Groening had been called to pitch a series of shorts based on his comic strip, 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 is an anagram of the word brat. After appearing on The Tracey Ullman Show for two years, the Simpson family received its own series on Fox, which debuted December 17, 1989. Bart has appeared in every Simpsons episode except "Four Great Women and a Manicure".

At ten years old, Bart is the eldest child and only son of Homer and Marge, and the brother of Lisa and Maggie. Bart's most prominent and popular character traits are his mischievousness, rebelliousness and disrespect for authority. Hallmarks of the character include his chalkboard gags in the opening sequence; his prank calls to Moe; and his catchphrases "Eat my shorts", "¡Ay, caramba!", "Don't have a cow, man!", and "I'm Bart Simpson. Who the hell are you?" However, with the exception of "¡Ay, caramba!", these hallmarks have been retired or are not often used. Bart 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, Cartwright originally planned to audition for the role of Lisa, while Yeardley Smith tried out for Bart. Smith's voice was considered too high for a boy, so she was given the role of Lisa. Cartwright found Lisa uninteresting, so she instead auditioned for Bart, which she thought was a better role.

During the first two seasons of The Simpsons, Bart was the show's protagonist and "Bartmania" ensued, spawning Bart Simpson-themed merchandise touting his rebellious attitude and pride at underachieving, which caused many parents and educators to cast him as a bad role model for children. Around the third season, the role of the protagonist was taken over by his father, and series started to focus more on the family as a whole, though Bart still remains a prominent breakout character. Time named Bart one of the 100 most important people of the 20th century, and he was named "entertainer of the year" in 1990 by Entertainment Weekly. Cartwright has won several awards for voicing Bart, including a Primetime Emmy Award in 1992 and an Annie Award in 1995. In 2000, Bart, along with the rest of his family, was awarded a star on the Hollywood Walk of Fame.