This book is a mix of engineering, operations research, and policy sciences intended to provide students with a thorough understanding of the concept of sustainability and sustainable product life-cycles, and an appreciation of the importance of sustaining critical systems. It starts from the key attributes for system sustainment that includes data analytics, engineering analysis and the public policy needed to support the development of technologies, processes, and frameworks required for the management of sustainable processes and practices. The specific topics covered include: acquisition of critical systems, reliability, maintenance, availability, readiness, inventory management, supply-chain management and risks, contracting for sustainment, and various analysis methodologies (discounted cash flow analysis, discrete-event simulation and Monte Carlo methods). Practice problems are included at the end of each chapter.