This chapter explores the foundational principles and practical applications of Systems Thinking and System Dynamics, emphasizing their critical value in understanding and managing complex systems, particularly in healthcare. Rejecting reductionist approaches that isolate variables, Systems Thinking promotes a holistic view where interconnections, feedback loops, and time delays reveal how changes in one area can have far-reaching, sometimes paradoxical, effects. System Dynamics operationalizes this perspective through modeling and simulation, enabling stakeholders to anticipate the long-term consequences of decisions before implementing them. The chapter traces the evolution of these frameworks from their theoretical roots in engineering and ecology to real-world applications in urban planning, supply chains, and environmental policy. It then delves into their adoption within the healthcare sector, illustrating how hospital operations, public health policy, and patient care have all benefited from this systemic lens. Case studies highlight how modeling tools can illuminate hidden inefficiencies in emergency departments and surgical suites, reduce readmissions, and inform resource allocation strategies. By uncovering the interdependencies that shape healthcare delivery, these frameworks foster a culture of continuous learning and adaptation. Ultimately, Systems Thinking and System Dynamics offer healthcare leaders robust tools to design more effective, sustainable interventions in a world of increasing complexity and limited resources.