WASP-21 is a G-type star (spectral type G3V) that is reaching the end of its main sequence lifetime[4][5] approximately 850 light years from Earth in the constellation of Pegasus.

The star is relatively metal-poor, having 40% of heavy elements compared to the Sun.

[7] In 2019 the WASP-21 system was chosen as part of the NameExoWorlds campaign organised by the International Astronomical Union, which assigned each country a star and planet to be named.

Transit-timing variation analysis in 2015 did not find an additional planets in the system.

[5] In 2020, spectroscopic analysis has found the WASP-21 b atmosphere is mostly cloudless and contains sodium.