On April 13th, 2019, OpenAI Five became the first AI system to defeat world champions at an e-sports game. The game of Dota 2 presents novel challenges for AI systems - such as long time horizons, imperfect information, and complex, continuous state-action spaces - all challenges which will become increasingly central to more capable AI systems. By defeating Team OG, the Dota 2 world champion, OpenAI Five demonstrates that self-play reinforcement learning can achieve superhuman performance on a difficult task.