Traditionally, $p$-adic $L$-functions have been constructed from complex $L$-functions via special values and Iwasawa theory. In this volume, Perrin-Riou presents a theory of $p$-adic $L$-functions coming directly from $p$-adic Galois representations (or, more generally, from motives). This theory encompasses, in particular, a construction of the module of $p$-adic $L$-functions via the arithmetic theory and a conjectural defmition of the $p$-adic $L$-function via its special values. Since the original publication of this book in French (Astérisque 229, 1995), the field has undergone significant progress. These advances are noted in this English edition. Also, some minor improvements have been made to the text.