This chapter introduces cognitive diplomacy as a novel model of statecraft that integrates human judgment with artificial intelligence to enhance decision-making, communication, and strategic influence in international relations. In a technopolar world shaped by algorithmic governance, platform politics, and digital asymmetry, diplomacy must evolve to address new cognitive and informational challenges. Cognitive diplomacy emerges as a strategic response to this shift, enabling states to project influence, process complex data, and defend epistemic sovereignty. Grounded in international relations theory—realism, liberalism, and constructivism—the chapter articulates cognitive diplomacy as both a theoretical framework and an operational strategy. It analyzes how AI technologies such as machine learning, natural language processing, and predictive analytics augment diplomatic functions, from public engagement to crisis anticipation. The chapter presents a three-pillar framework: cognitive presence, cognitive practice, and cognitive resilience, each linked to specific diplomatic capacities and illustrated through real-world applications from countries like the United States, China, Estonia, and Türkiye. While promising, the integration of AI into diplomacy also raises ethical and normative concerns, including algorithmic bias, accountability, and sovereignty erosion. Ultimately, the chapter argues that cognitive diplomacy is essential for achieving digital autonomy, allowing states to navigate the cognitive frontiers of twenty-first-century power while safeguarding democratic agency and strategic foresight.