  These lectures provide an overview of Quantum Chromodynamics (QCD), the SU(3)
gauge theory of the strong interactions. The running of the strong coupling and
the associated property of Asymptotic Freedom are analyzed. Some selected
experimental tests and the present knowledge of $\alpha_s$ and the quark masses
are briefly summarized. A short description of the QCD flavour symmetries and
the dynamical breaking of chiral symmetry is also given.
