Homestuck is an Internet fiction multimedia series created by American author and artist Andrew Hussie. The fourth and best-known of Hussie's four MS Paint Adventures, it originally ran from April 13, 2009, to April 13, 2016. Though normally described as a webcomic, and partly constituted by a series of single panel pages, Homestuck also relies heavily on Flash animations and instant message logs to convey its story, along with the occasional use of browser games.

Its plot begins with a group of teens who trigger the destruction of Earth by installing the beta version of an upcoming PC game, Sburb. The teens soon come into contact with a group of Internet trolls who are revealed to be horned aliens, and these trolls work with the teens to create a new universe by completing the game. It has been noted for its complex and nonlinear narrative, considerable length at over 8,000 pages and 800,000 words, and intensely devoted fan community.

The success of Homestuck has resulted in numerous related projects and sequels, including the Hiveswap series of adventure games. On August 9, 2025, an animated web series pilot adaptation was announced by Vivienne Medrano's company SpindleRoo, an Australian division of SpindleHorse, with Skye Henwood as director and writer. Released on September 27, 2025, the pilot stars Toby Fox, Cherami Leigh, Colleen O'Shaughnessey, Adam McArthur, Chris O'Neill, and Brandon Winckler.

In 2009, on John Egbert's thirteenth birthday, he receives a beta copy of a mysterious computer game called Sburb, which he can use to manipulate the real world through a sandbox game style interface. John's friends—Rose Lalonde, Dave Strider, and Jade Harley—join him in the game, which causes massive meteor storms to appear that target each of their homes. They only escape by completing tasks in the game until they are able to travel to a place called "the Medium", and they learn that installing Sburb has somehow triggered the destruction of Earth, and that they must beat the game to create a new universe.

While exploring the Medium, John and his friends are attacked by a ruthless villain known as Jack Noir. John and his friends are also harassed by a group of twelve Internet trolls whose own session of Sburb ended in failure, for which they blame the kids. Among the trolls, Karkat Vantas, Kanaya Maryam, Terezi Pyrope, and Vriska Serket each develop a relationship with the four humans, and the trolls are revealed to be an actual species of troll-like aliens. The narrative shifts to a side story arc about the trolls and the specific sequence of events that led this group to play their own session of the game. The enigmatic Doc Scratch, who serves an even more mysterious master, manipulated the trolls. The trolls eventually win their session and a new universe – the universe the kids inhabit – is created. Before they can claim their prize, they are attacked by Jack Noir and forced into hiding on a meteor, where they begin to troll the kids via a chat program.

Returning to the present, the two species cooperate to salvage the kids' game session. However, Vriska sabotages key events, resulting in the kids accidentally transforming Jack Noir into a seemingly invincible monster. Rising tensions among the trolls eventually boil over, and some begin to attack and kill the others; almost half the group (including Vriska) dies before Karkat manages to restore order. From Doc Scratch, the kids learn about a game mechanism called the "Scratch" that allows the humans to reset their session to escape Jack but will also inadvertently summon Lord English, Doc Scratch's master who seeks dominion over all of reality.

Executing the Scratch resets the kids' universe, and versions of themselves become guardians to a new group of players, who are versions of their own ancestors. As a result, John's late grandmother, Jane Crocker, is fifteen years old and the protagonist of the new arc. She leads her three friends Roxy Lalonde, Dirk Strider, and Jake English—Rose's mother, Dave's brother, and Jade's grandfather, respectively—through their own session of the game, while the original humans and surviving trolls journey through dimensions to the new post-Scratch session over the course of three years.

The post-Scratch version of Earth quickly becomes dominated by Her Imperious Condescension (aka the Condesce), the sinister former troll empress now in service to Lord English. In lieu of trolls, the four post-Scratch kids interact online with one* alien cherub, the siblings Calliope and Caliborn. While Calliope becomes a fast friend of the group, Caliborn resents their camaraderie, and is highly antagonistic towards them. After the post-Scratch kids enter their session, the two cherubs play their own version of Sburb in a session that sees Caliborn having his sister assassinated so that he may be the sole winner of the game.