Let p be a prime. The subject of this thesis is the p-adic Langlands correspondence. If V is a p-adic representation of dimension 2 of the group Gal(\bar{Qp}/Qp), it is known how to associate to it a continuous p-adic representation B(V) of GL₂(Qp). If F is a non-trivial finite extension of Qp, the issue of associating p-adic representations of GL₂(F) to p-adic representations of dimension 2 of Gal(\bar{Qp}/F) in the spirit of a local Langlands correspondence appears much more delicate. In this text we consider a class of p-adic Banach spaces, endowed with a continuous linear action of GL₂(F), which are obtained as universal unitary completions of certain locally Qp-analytic representations of GL₂(F). Such representations are likely to play an important role in a future local p-adic Langlands correspondence for GL₂(F). The main result of this thesis is proved in Chapter 3 and generalizes some previous results of Berger and Breuil. It consists in an explicit description of these universal unitary completions by means of a certain class of continuous functions on F. In order to do this, we introduce in Chapter 2 a class of Banach spaces of functions of class C^r, where r is a positive rational number, as well as their dual spaces of distributions of order r. We build a Banach base and we give a criterion for telling when a linear form defined on a space of locally Qp-polynomial functions extends to a distribution of order r. As a consequence, we generalize some classical results due to Amice-Vélu and Vishik. In Chapter 4 we exhibit cases of non-nullity for these universal unitary completions, by an explicit construction of invariant lattices. This also provides new instances of the Breuil-Schneider conjecture about the equivalence between the existence of invariant norms on certain locally algebraic representations of GL_d(F) and the existence of certain De Rham representations of Gal(\bar{Qp}/F).
