  The first determination of the surface temperature of stars other than the
Sun is due to the Hungarian astrophysicist B\'ela Hark\'anyi. Prompted by the
recent unprecedented increase in the availability of stellar temperature
estimates from Gaia, coinciding with the 150th anniversary of Hark\'anyi's
birth, this article presents the life and work of this neglected, yet
remarkable figure in the context of the history of stellar astrophysics.
