John "J." Jonah Jameson Jr. is a fictional character appearing in American comic books published by Marvel Comics, most commonly in association with the superhero Spider-Man. The character was created by writer Stan Lee and artist Steve Ditko, and he first appeared in The Amazing Spider-Man issue #1 (March 1963).

Jameson is typically depicted as the publisher or editor-in-chief of the Daily Bugle, a fictional New York City newspaper. Recognizable by his toothbrush moustache, flattop haircut, and ever-present cigar, he carries out a smear campaign against Spider-Man (and to a lesser extent other superheroes such as Daredevil), frequently referring to him as a "menace" and a criminal, but occasionally and reluctantly allying with him. This usually stems from his deep-seated belief in law enforcement and government agencies, and thus despises superheroes for working outside the system. In the early comics as well as most media interpretations, he employs photojournalist Peter Parker to take pictures of Spider-Man in the hopes of catching him in the middle of wrongdoing, unaware that Peter is the superhero himself. Over the course of the comics, Jameson has done various other jobs, most notably being the Mayor of New York City for several years before resigning. Peter has revealed his identity to Jameson twice: the first during the "Civil War" event, which was undone by the events of the "One More Day"; and the second years later, which caused him to finally give up his crusade on Spider-Man and become a permanent ally and advocate of him.

Portrayals of Jameson in both the comics and external media have varied throughout the years. Sometimes he is shown as a foolishly grumpy, stubborn and pompous micromanager whose resentment of Spider-Man is actually a thinly-veiled exercise in envy. Other writers have portrayed him more empathetically, as a humorously obnoxious yet caring boss and family man who nevertheless has shown great bravery and integrity in the face of the assorted villains with which the Bugle comes into contact, and whose campaign against Spider-Man comes more from the aforementioned political motivations. He and Peter Parker are related by marriage as a result of his father's wedding to May Parker. Jameson's son John Jameson is a Marvel Universe supporting character who, in addition to his job as a famous astronaut, has become Man-Wolf and Star-God and also married She-Hulk, making Jonah her father-in-law before she and John divorced. In addition to Man-Wolf, he also serves as a principal figure in the creation of Spider-Man foes Spider-Slayer and Scorpion.

The character has appeared in numerous media adaptations related to Spider-Man; he usually assumes his early role as Peter's employer, but this has lessened in recent years as depictions of Spider-Man focused around his science and superhero careers, with Jameson simply being Spider-Man's tormentor. Most famously, J. K. Simmons portrayed the character in Sam Raimi's Spider-Man trilogy (2002–2007) and in the Marvel Cinematic Universe films Spider-Man: Far From Home (2019) and Spider-Man: No Way Home (2021). Simmons also voices him in various additional works, such as Ultimate Spider-Man.