Résumé
A large number of observations suggest that our universe entered at low redshifts a stage with accelerated expansion rate. Many models, Dark Energy (DE) models, able to explain this departure from conventional cosmology have been proposed. These models are conceptually very different, either introducing some new component with sufficiently negative pressure, or modifying the gravitational interaction on cosmic scales. Some of these DE models are reviewed here. Future high precision observations probing both the background and the perturbations will single out viable models.