This chapter examines the transformative effects of generative AI (GenAI) on competition law, exploring how GenAI challenges traditional business models and antitrust regulations. The evolving digital economy, characterised by advances in deep learning and foundation models, presents unique regulatory challenges due to market power concentration and data control. This chapter analyses the approaches adopted by the European Union, United States, and United Kingdom to regulate the GenAI ecosystem, including recent legislation such as the EU Digital Markets Act, the AI Act, and the US Executive Order on AI. It also considers foundational models’ reliance on key resources, such as data, computing power, and human expertise, which shape competitive dynamics across the AI market. Challenges at different levels—including infrastructure, data, and applications—are investigated, with a focus on their implications for fair competition and market access. The chapter concludes by offering insights into the balance needed between fostering innovation and mitigating the risks of monopolisation, ensuring that GenAI contributes to a competitive and inclusive market environment.