New forms of computation enable fundamentally new kinds of virtual Worlds. Autonomous Worlds are not just Worlds that happen to exist onchain, but Worlds that could not exist otherwise. Personal computing allowed early game developers to sculpt single-player Worlds in which isolated individuals could immerse themselves in the rule-based structure of a text adventure or a pixel bouncing around the screen. Networked computing allowed for these private interactive experiences to be expanded into multiplayer Worlds: server-based muti-user dungeons and massively multiplayer online games whose dynamic unfolding was no longer contingent on the participation of a single player.The arrival of onchain computing brings with it the possibility of Autonomous Worlds: multi-author, maximally persistent Worlds that can not only be experienced by multiple inhabitants, but also expanded by them. These Worlds are no longer read-only vessels for private immersion or collective experience, but a collaborative commons whose open-ended evolution is steered by digital consensus.The unique affordances of Autonomous Worlds can be glimpsed in early experiments with onchain games, but their full potential remains to be realized. In this hackathon, we invite developers and game designers to build games and tooling that test what they see as the fullest possible expression of an Autonomous World.