GPUSPH is an open-source C++/CUDA code for the simulation of 3D fluid flow. The fluid is modeled by Smoothed Particle Hydrodynamics (SPH), which is a mesh-free Lagrange particle method, first described by Lucy (1977) and Gingold and Monahan (1977). It was the first SPH code to use graphics cards (GPU) for computation. GPUSPH was described by Alexis Hérault, Giuseppe Bilotta, and Robert Dalrymple (“SPH on GPU with CUDA,” Journal of Hydraulic Research, 48, 74-79, 2010) and has been used for a variety of free surface flow problems. The code is available from gpusph.org.