RS Persei is a red supergiant variable star located in the Double Cluster in Perseus.

The star's apparent magnitude varies from 7.82 to 10.0, meaning it is never visible to the naked eye.

[11] RS Persei is a large cool star with a temperature of 3,500 K. Its size makes it luminous, although much of its radiation is emitted in the infrared.

[6] More recently, across all wavelengths gives the star a lower luminosity of 77,600+9,500−8,400 L☉, and a radius of 770±30 R☉ based on the distance and the measured angular diameter by the CHARA array.

[14] RS Persei has sometimes been considered to be a highly evolved low mass Asymptotic Giant Branch (AGB) star,[15] but calculations of its current mass suggest that it is a true red supergiant.