The BerkeleyGW package is a set of computer codes that calculates the quasiparticle properties and the optical responses of a large variety of materials from bulk periodic crystals to nanostructures such as slabs, wires and molecules. The package takes as input the mean-field results from various electronic structure codes such as the Kohn-Sham DFT eigenvalues and eigenvectors computed with PARATEC, Quantum ESPRESSO, SIESTA, PARSEC, Abinit, Octopus, or TBPW (aka EPM). The package consists of the three main component codes: * Epsilon computes the irreducible polarizability in the Random Phase Approximation and uses it to generate the dielectric matrix and its inverse. * Sigma computes the self-energy corrections to the DFT eigenenergies using the GW approximation of Hedin and Lundqvist, applying the first-principles methodology of Hybertsen and Louie within the generalized plasmon-pole model for the frequency-dependent dielectric matrix. * BSE solves the Bethe-Salpeter equation for correlated electron-hole excitations. WWW: https://berkeleygw.org