Today's most pressing security and policy challenges-great power conflict, economic interdependence, peacebuilding, climate change and other non-traditional threats such as pandemics-are all complex problems. Hyperconnectivity, power diffusion and radical technological transformation are significantly shrinking the policy space available to governments and other international agencies in what has been called the twenty-first century of complexity. Thus, the practice of statecraft requires accentuated strategic rationale: clear emphasis on big-picture and longer-term purposes and priorities. While effective strategy is essential for mobilizing power and winning strategic contests, effective diplomacy is necessary for garnering support for the strategy. This article contributes to stepping up to this challenge in three innovative ways. First, it utilizes key insights from complex adaptive systems thinking to recast the conceptual underpinnings of power, strategy and statecraft. Second, the article advances a 'strategic diplomacy' diagnostic and policy framework to maximize policy space in dealing with complex systems problems in international affairs. And third, by applying the framework to three significant international policy challenges, the article demonstrates the utility and implications of the 'strategic diplomacy' framework for strategic policy in the twenty-first century. Our world today plays host to complex international relations where threats are global, and countries are interdependent. Against this backdrop, nations should re-imagine strategy and statecraft. The authors apply a 'strategic diplomacy' framework to competition in Asia to show its utility.