Varietes de Fano et morphismes: notes d'un mini-cours

This is not a research article. This is a partial version of a mini-cours which I gave at a meeting of the ACI Jeunes Chercheurs "Dynamique des applications polynomiales" in Toulouse in november 2004. This text includes two parts of that mini-cours: the first one collects some preliminaries on Fano threefolds with cyclic Picard group, the second one discusses some methods to obtain bounds for the degree of a morphism onto such a Fano threefold (different from projective space). The mini-cours also had a third part - the boundedness theorem of Hwang and Mok for morphisms between Fano manifolds which have rational curves with trivial normal bundles; this part is not included here, as the Hwang and Mok's paper in Journal of Algebraic Geometry 12 (2003) is concise, clear and self-contained.