Résumé : In the theory of von Neumann algebras, some of the most important classes of examples come from discrete countable groups, their actions on measure spaces, and countable Borel equivalence relations. Introduced by Mackey in 1963, measured groupoids provide a unified framework to study all of these classes at once. However, it was not known whether there exists a 'genuine' measured groupoid that is not isomorphic to one from any of these known classes. In this talk, we shall see that we can indeed construct a large class of genuine groupoids, and we can do so in such a way that the associated von Neumann algebras are factors.