  We present an efficient approach to the electron correlation problem that is
well-suited for strongly interacting many-body systems, but requires only
mean-field-like computational cost. %which is based on orbital optimization of
electron pairs. The performance of our approach is illustrated for the
one-dimensional Hubbard model with periodic boundary conditions for different
chain lengths, and for the non-relativistic quantum chemical Hamiltonian
exploring the symmetric dissociation of the H$_{50}$ hydrogen chain.
