Particle acceleration in astrophysical collisionless shocks

I will review the properties of astrophysical shocks related to their roles as accelerators of energetic particles. Ab-initio simulations of collisionless shock structure reveal different regimes of particle injection and acceleration as a function of shock parameters, including magnetization of the flow and magnetic geometry in the upstream. These regimes can be used to interpret high-energy observations of astrophysical sources, such as supernova remnants and gamma-ray bursts, and can guide the design of experiments to study shock acceleration physics in the laboratory.