Until now, the basic results on algebraic stacks were scattered in the literature and sometimes stated without proofs. This book - written in French -- fills this reference gap by providing mathematicians with the first systematic account of the general theory of (quasiseparated) algebraic stacks over an arbitrary base scheme. It covers the basic definitions and constructions, techniques for extending scheme-theoretic notions to stacks, Artins representability theorems, but also such new topics as the "lisse-tale" topology.