This book provides an introduction to Quantum Chromodynamics (QCD), the theory of strong interactions. It covers in full detail both the theoretical foundations and the experimental tests of the theory. Although the experimental chapters focus on recent measurements, the subject is placed into historical perspective by also summarizing the steps which lead to the formulation of QCD. Measurements are discussed as they were performing by the LEP experiments at CERN, or at hadron-hadron and lepton-hadron colliders such as the TEVATRON at Fermilab and HERN at DESY. Emphasis is placed on high...