This chapter introduces the concept of complexity in modern decision-making, focusing on its increasing relevance in today’s interconnected and dynamic environments. Complexity is defined through its core attributes, including unpredictability, interdependencies, and emergent behaviors. The chapter explores how artificial intelligence (AI) and systems thinking can be synergistically employed to address these challenges, providing decision-makers with tools to navigate and mitigate complex scenarios effectively. The purpose and scope of the book are also outlined, emphasizing the integration of AI and systems thinking as a novel approach to smarter decision-making in complex contexts.