Jointly modeling relative astrometry of HIP 99770 b with absolute astrometry of the primary as measured by Gaia and Hipparcos yields precise estimates for the companion's orbit and mass. HIP 99770 b lies at about 16.9 au from its host star. The host star is significantly more luminous than the Sun: HIP 99770 b receives roughly as much light as Jupiter receives from the Sun. HIP 99770 b is a super-jovian planet with a mass of roughly 16.1 times that of Jupiter. Its mass ratio -- mass divided by the mass of the host star -- is comparable to that of many planets detected through methods such as radial velocity and transits and is similar to that of HR 8799 d.
