This book is a collection of eight chapters which provide an overview of what one should know about hydroxyapatite (Ha). Chapter One reviews the modification of hydroxyapatite coatings for implant applications. Chapter Two discusses the removal of pollutants by means of hydroxyapatite composites. Chapter Three reviews the synthesis and characterization of hydroxyapatite. Chapter four explores the potential use of functionalized hydroxyapatite in bone regeneration. Chapter Five reviews the applications of modified hydroxyapatite in catalysis. Chapter Six examines hydroxyapatite in terms of sustainable product development and waste valorization. Chapter Seven reviews the deposition of Ha-based coatings on bio-inert substrates by various deposition methods for improved bio-mechanical properties. Chapter Eight explores 3D printed Ha ceramics and its composite scaffolds for tissue engineering.