In 2007 the HATNet Project reported the discovery of HAT-P-3b transiting the metal-rich early K dwarf star HAT-P-3 with an orbital period of 2.9 days. It was found with the 11 cm aperture HAT-5 telescope, located at the Fred Lawrence Whipple Observatory on Mount Hopkins in Arizona. Follow up radial velocity observations to confirm the planet were made with the 1.5 m Tillinghast reflector in order to rule out the possibility that the observed decrease in brightness was caused by an eclipsing binary. Final confirmation was made at the W. M. Keck Observatory using the HIRES spectrograph to measure the mass and orbital parameters of the planet.