Sapphire++ (Simulating astrophysical plasmas and particles with highly relativistic energies in C++) numerically solves the Vlasov–Fokker–Planck equation for astrophysical applications. It employs a numerical algorithm based on a spherical harmonic expansion of the distribution function, expressing the Vlasov–Fokker–Planck equation as a system of partial differential equations governing the evolution of the expansion coefficients. The code uses the discontinuous Galerkin method in conjunction with implicit and explicit time stepping methods to compute these coefficients, providing significant flexibility in its choice of spatial and temporal accuracy.