Jhonen C. Vasquez (/ˈdʒoʊ.nɛn ˈvæs.kɛz/; born September 1, 1974) is an American cartoonist and animator. His work includes creating the Nickelodeon animated series Invader Zim and its namesake comic book series, creating the comic book series Johnny the Homicidal Maniac and its spin-offs like Squee! and I Feel Sick, and directing music videos for bands such as Mindless Self Indulgence.

Jhonen C. Vasquez was born in San Jose, California, on September 1, 1974. He is of Mexican descent. He grew up in East San Jose and attended Mt. Pleasant High School, where he spent much of his class time drawing in notebooks. A fan of Disney animated features, he found himself even more fascinated by alternative animation from filmmakers such as Ralph Bakshi. He later cited The Plague Dogs and Flight of Dragons as two of the most personally influential animated films he saw as a child, while Alien was the live-action work that influenced him the most.

Vasquez also read his older brother's superhero comics as a child, but first became interested in exploring the medium through the original Teenage Mutant Ninja Turtles comics by Peter Laird and Kevin Eastman. He later said, "There was something just so different about those [Ninja Turtles comics] that I did start to obsess over them—the way the books felt dirtier in my hands, the filthy artwork and hero characters that never seemed healed over from their last battles. There was a sense of person just behind the printed page that I had never felt before, a thinner separation from production to my hands and eyes [...] it's like, the book itself was less removed from the initial moment a creator is excited about having just come up with some great idea to when they finally finish a thing, nice and polished and just a little dulled from before the thing was just another book."

During high school, Vasquez took part in a contest to design a new look for his school's mascot. He earned no prizes; however, on the back of a preliminary drawing for the contest, he drew his first sketch of who would later become the title character of Johnny the Homicidal Maniac, and the student newspaper published a number of his comic strips featuring Johnny. He also created Happy Noodle Boy while attending Mt. Pleasant. After graduating in 1992, he became a film student at De Anza College in Cupertino, California. Despite having little formal artistic training, he soon dropped out of De Anza to pursue a career as a professional cartoonist. He met Roman Dirge and Rosearik Rikki Simons at Alternative Press Expo in 1995; the former became a writer on Vasquez's series Invader Zim, while the latter voiced the protagonist's robot sidekick GIR and joined the show's coloring team. Simons also worked with Vasquez on the coloring seen in his two-issue comic I Feel Sick. In September 1996, Vasquez announced in his introductory text to the sixth issue of Johnny the Homicidal Maniac that the comic book had become successful enough for him to quit his day job.

Carpe Noctem magazine published early one-page strips featuring Johnny in the early 1990s. In 1995, Slave Labor Graphics began publishing a series of Johnny comics after Vasquez submitted samples of his artwork to them. Vasquez's first comic, Johnny the Homicidal Maniac, ran for seven issues and was collected as a hardcover and a trade paperback book named Johnny the Homicidal Maniac: Director's Cut. The cover features the logo "Z?", meaning "question sleep", which appears frequently throughout Vasquez's work and relates to his characters' insomnia and his own hypnophobia. The series follows Johnny as he searches for meaning in his life, a quest that frequently leads to the violent deaths of those around him as well as, briefly, his own. A photograph of one of Vasquez's friends, Leah England, serves as the middle of a portrait collection on the cover for the second issue of Johnny the Homicidal Maniac. England also gave Vasquez the inspiration for a filler strip about a child who was dangerously afraid of losing sight of his mother, as well as the notorious "Meanwhile" filler piece in the second issue of Johnny the Homicidal Maniac. Vasquez's next project was The Bad Art Collection, a 16-page one-shot comic. He stated that he did the book's art while he was in high school to discourage classmates from asking him to draw for them.

In 1997, Vasquez gave Squee, a supporting character from Johnny the Homicidal Maniac, his own four-issue series. It chronicles Squee's encounters with aliens, Satan's son, and eventually Satan himself. The trade version (which features a cover image of Squee with the words "Buy me or I'll die!") contains, in addition to the actual Squee comics, the Meanwhiles that were left out of the Director's Cut of Johnny the Homicidal Maniac, as well as comics of Vasquez's "real life" and Wobbly-Headed Bob. Vasquez's next project was I Feel Sick, colored by Rikki Simons. I Feel Sick follows a tortured artist named Devi (another character introduced in Johnny the Homicidal Maniac) as she tries to maintain her sanity in an insane vision of society, despite conversing with Sickness, one of her own paintings. Slave Labor has published three Fillerbunny mini-comics, the third having been released in March 2005. The Mini-Comic was a spin-off of a filler comic designed to replace a vacant page usually reserved for advertising space in the Squee! comics.

Vasquez said at the 2007 New York Comic Con that the original Fillerbunny comics would be done in a single night and he would rush through and do whatever he could in a small amount of time. The third issue, however, broke this mold. According to the introduction, it took over nine months to complete, and he feels it is of much higher quality than the first two. At Comic-Con 2005, Vasquez mentioned that his next comic was a love story. Since this, however, he attended an event in early 2007 and stated he was not working on his "own" comics – he was collaborating on two comics in the style of Everything Can Be Beaten, acting only as author. The first, titled Jellyfist, was intended for release on July 25, 2007, but the initial print run of Jellyfist was incredibly poor, and so it was re-released in October 2007. In 2009, Vasquez collaborated with other alternative artists in Marvel Comics' Strange Tales, issue 2 of 3, with a story about MODOK. It sold extremely well and all three issues have been collected into a hardcover trade paperback. The next year he returned for Marvel's Strange Tales II, issue 1 of 3, with a story about Wolverine.

In 2012, DC Comics announced that Vasquez joined the writing team for their digital comic Beyond the Fringe, based on the Fox TV series Fringe. In May 2014, Vasquez announced on his Tumblr page that he would be re-releasing his previous Fillerbunny comics into a new collection and additionally releasing his first new comic book in ten years.