This book is a tribute to Harald Fritzsch (1943-2022), who has made outstanding contributions to the development of modern particle physics. He was a pioneer of QCD, the gauge theory of strong interactions, and contributed significantly to Grand Unified Theories and to the physics of quark and lepton flavors.The present book collects reminiscences of Harald Fritzsch and scientific articles, written by friends, colleagues, collaborators and former students. The contributed articles span a wide range of topics, reflecting Harald's broad interests in physics, from QCD and its applications at high and low energies, the flavor puzzle, flavor symmetries and textures, to gravity, constants of Nature and fundamental symmetries and their violation. The authors of these articles include, among others, Siegfried Bethke, Johannes Bluemlein, Stanley J Brodsky, Gerard 't Hooft, Heinrich Leutwyler, Hans Peter Nilles, Serguey T Petcov, Kok Khoo Phua and Willibald Plessas.