Gliese 806 is a star in the northern constellation of Cygnus, located about a degree to the southeast of the bright star Deneb.^[9] It is invisible to the naked eye with an apparent visual magnitude of +10.79.^[2] The star is located at a distance of 39.3 light years from the Sun based on stellar parallax.^[1] It is drifting closer with a radial velocity of −24.6 km/s, and is predicted to come to within 30.1 light-years in ~198,600 years.^[10] The star hosts two known planetary companions.^[4]

The stellar classification of Gliese 806 is dM1.5,^[3] which indicates this is a small red dwarf star – an M-type main-sequence star that is generating energy through core hydrogen fusion. It is roughly three^[6] billion years old and is spinning with a projected rotational velocity of 0.46 km/s.^[5] The star has 42% of the mass and radius of the Sun. It is radiating 0.3% of the luminosity of the Sun from its photosphere at an effective temperature of 3,586 K.^[3]

In 1989, Marcy and Benitz detected a periodicity of 416 days in radial velocity variation, inferring the possible presence of a companion with a mass of about 0.011 M_☉.^[11] However, this candidate object was never confirmed.

More recently, observations by TESS have found a candidate transiting planet with a period of less than a day.^[8] In January 2023, this planet was confirmed and a second, non-transiting planet found via radial velocity observations. A third radial velocity signal was also found, but the study was unable to confirm it as having a planetary origin. All known planets are super-Earths, and the inner transiting planet Gliese 806 b is likely to be rocky.^[4]

• Gliese 521