We present the discovery and characterization of a giant planet companion to the young, nearby star AF Lep. AF Lep is a member of the beta Pictoris moving group, and was identified as an accelerating star from a combination of Hipparcos and Gaia data. Using VLT/SPHERE we confirmed the acceleration is due to a giant planet between 4-6 Jupiter masses orbiting 9 au from the star. Photometry and spectroscopy from the discovery dataset produce a model-dependent mass consistent with the dynamical mass from the orbit fit. Along with planets 51 Eridani b and beta Pic b and c, as well as brown dwarf companions PZ Tel B and HR 7329 B, AF Lep fills out an important mass sequence of coeval benchmark substellar companions.