Qbox is a First-Principles Molecular Dynamics code. It can be used to compute the electronic structure of atoms, molecules, solids and liquids within the Density Functional Theory (DFT) formalism. It can also be used to perform first-principles molecular dynamics (FPMD) simulations using forces computed within DFT. Qbox computes the solutions of the Kohn-Sham equations using a plane-wave basis set and norm-conserving pseudopotentials. It can perform constant-temperature and/or constant-pressure simulations.