This book explores how mission outcomes are shaped through deliberate engineering and operational decisions involving heterogeneous systems and diverse stakeholder communities. Mission Engineering and Integration (MEI) is the discipline that ensures these efforts are not only technically sound, but also operationally effective, risk-informed, and economically viable. From decomposing mission objectives and defining clear success criteria, to managing risk, enabling human-machine collaboration, and designing for adaptability, it delves into the principles and practices that drive high performance in demanding environments. Applicable across a range of industries—including defense, transportation, energy, and healthcare —Mission Engineering and Integration provides a practical roadmap for decision-makers, engineers, and strategists working to deliver resilient, responsive, and effective system-of-systems in an increasingly dynamic and interdependent world.