"Radio Bart" is the thirteenth episode of the third season of the American animated television series The Simpsons. It originally aired on Fox in the United States on January 9, 1992. In the episode, Bart receives a microphone that transmits sound to nearby AM radios. To play a prank on the citizens of Springfield, he lowers a radio down a well and uses the microphone to trick the town into thinking a little boy is trapped there. The prank succeeds, but Bart remembers labelling the radio with his name, tries to retrieve it, and becomes trapped himself. Angry at being duped by Bart, the townspeople refuse to rescue him.

The episode was written by Jon Vitti and directed by Carlos Baeza. Musician Sting guest starred in the episode as himself, though the producers originally approached Bruce Springsteen to appear. The episode features cultural references to charity singles such as "We Are the World". Since airing, "Radio Bart" has received a positive critical reception from television critics.

It acquired a Nielsen rating of 14.1 and was the highest-rated show on Fox the week it aired. It was nominated for an Emmy Award but lost to A Claymation Easter.

Homer sees a television commercial for the Superstar Celebrity Microphone — which can broadcast anyone's voice over AM radio — and impulsively buys one for Bart's birthday. At his party, Bart is crestfallen when he receives gifts such as a cactus, a label maker, and a new suit. At first, Bart dislikes the microphone, but he later uses it to play practical jokes, such as tricking Ned's sons, Rod and Todd, into believing that God is talking to them, eavesdropping on Lisa and Janey's conversations about boys, and convincing Homer that Martians are invading. He also uses the microphone to make it look like Mrs. Krabappel made flatulent noises.

Bart ends up losing the radio down a well, but plays this to his advantage, tricking the townspeople into thinking an orphan named Timmy O'Toole has fallen down the well. Although they are unable to rescue Timmy, since the well is too small to accommodate an adult, the entire town offers its love and moral support. Krusty persuades Sting to join other celebrities in recording a charity single, "We're Sending Our Love Down the Well".

Lisa catches Bart imitating Timmy's voice and reminds him that the townspeople will be angry at him for being duped, while correctly assuming that he put a "Property of Bart Simpson" label on the radio. Out of fear of reprisal, Bart tries to climb down in the well to retrieve the radio after nightfall but falls down to the bottom when police officers Eddie and Lou kicks the rope Bart used to lower himself down the well. When the townspeople find Bart trapped there, he admits Timmy does not exist. Angry at being tricked, the townspeople refuse to rescue him.

After a tearful speech by Bart saying that there would be many things he would miss out on including what would happen in the family, Homer has finally had enough and decides to dig a tunnel and rescue Bart himself. Groundskeeper Willie helps Homer dig and soon several other residents join the excavation, finally rescuing Bart with help from Sting. The next day, Willie posts a warning sign near the well to prevent future accidents.

"Radio Bart" was written by Jon Vitti and directed by Carlos Baeza, though series creator Matt Groening came up with the idea for it. The episode was based on the 1951 film Ace in the Hole, which sees the story of a down-and-out journalist exploiting a story about a man trapped in a cave to re-jump start his career. Vitti did not watch the film until after the episode had been written; "[Groening] came in out of nowhere and just gave me, start to finish, the whole story." Vitti said renting the film was the first thing he did after finishing the script. He remarked, "It's surprisingly hard to rent. It's really dark and funny and it's by Billy Wilder, so you think it would be in stores, but it's not. It was hard to find."