This book presents a comprehensive exploration of space debris from four essential perspectives: detection, early warning, protection, and mitigation. It begins with both ground-based and space-based detection technologies and systems, followed by an in-depth discussion on debris environment modeling, prediction principles, and early warning mechanisms. The book then addresses spacecraft shielding structures and protective materials, along with mission-level protection design. Finally, it covers mission planning strategies and active debris removal techniques for long-term mitigation. Policy frameworks, international regulatory efforts, and global collaboration initiatives are also examined to provide a complete context.This volume is ideal for undergraduate and graduate students, researchers, and engineers engaged in aerospace engineering, space safety, and orbital operations, offering both foundational theories and advanced methodologies.