Abstract We introduce a new slave‐boson mean‐field theory which allows the investigation of general multi‐band Hubbard models. Unlike earlier attempts of such a generalization, in our approach the quantum‐mechanical problem is exactly reformulated in an extended Hilbert space of Fermions and Bosons before a mean‐field approximation is applied. Systems with superconducting order parameters are naturally included in our formalism. Our ground‐state energy functional agrees with the corresponding quantity derived within the Gutzwiller theory.