HR 5983 is a sixth-magnitude composite-spectrum binary system. It has a circular orbit and a period of 108d. We separate the component spectra and show that they are of types ~G6IIIa and A2.5IV, with a mass ratio (giant:dwarf) of ~1.04. We find that the secondary has a mass close to 2.6Msolar and has already evolved somewhat from the main sequence, and that the primary appears to have reached the helium-burning `blue loop' stage and is in synchronous rotation. The system resembles Capella in several respects, and may represent an earlier phase in the evolution of the latter.