Systems with long-range forces behave very differently from those in which particles interact through short-range potentials. For systems with short-range forces, for arbitrary initial conditions, the final stationary state corresponds to the thermodynamic equilibrium and can be described equivalently by either a microcanonical, canonical, or a grand-canonical ensemble. On the other hand, for systems with unscreened long-range interactions equivalence between ensembles breaks down. In thermodynamic limit, an isolated system with long-range interactions become trapped in a non-ergodic stationary state which explicitly depends on the initial particle distribution. In this talk, a theoretical framework will be presented which allows us to obtain the final stationary state achieved by systems with long-range interactions. The theory is able to quantitatively predict both the density and the velocity distributions in the final stationary state, without any adjustable parameters.