GJ 3929, also known as Gliese 3929 and TOI-2013, is a red dwarf star located 51.6 light-years from Earth, in the constellation Corona Borealis.

[4] GJ 3929 is a red dwarf of spectral type M3.5V, having a radius of 0.32±0.01 R☉, a mass of 0.313+0.027−0.022 M☉ and a temperature of 3384±88 K.[6] With an apparent magnitude of 12.7,[2] it cannot be visible with the naked eye, neither with a small telescope.

[3] The star is located in the northern hemisphere, approximately 50 light years from Earth,[5] in the direction of the constellation Corona Borealis.

[3] Observations using the ARCTIC imager, plus photometry from TESS and LCOGT, constrained the planet's radius to 1.09±0.04 R🜨.

Due to the apparent brightness of the host star, and its small size, GJ 3929 b is an excellent planet for atmospheric study with the James Webb Space Telescope.

[7] Subsequent observations, mainly with the CARMENES spectrograph, revealed that this transit signal is an orbiting exoplanet.