  These lectures provide an overview of Quantum Chromodynamics (QCD), the
$SU(3)_C$ gauge theory of the strong interactions. After briefly reviewing the
empirical considerations which lead to the introduction of {\it colour}, the
QCD Lagrangian is discussed. The running of the strong coupling and the
associated property of {\it Asymptotic Freedom} are analyzed. Some selected
experimental tests and the present knowledge of $\alpha_s$ are summarized. A
short description of the QCD flavour symmetries and the {\it dynamical breaking
of chiral symmetry} is also given.
