The increasing importance of innovation competition requires adjusting the definition of an antitrust market. The article considers how technological change affects the economic definition of a market. The article examines both the 2023 Department of Justice and Federal Trade Commission Merger Guidelines and the 2024 European Commission Notice on the definition of a relevant market. The article explains that the 2023 Guidelines’ proposed market definition using worsening of innovation is misguided. The article presents a comprehensive approach to the economic definition of a market and examines some of the effects of innovation. The article argues that antitrust market definition should address innovation and technological change.