RR Coronae Borealis (RR CrB, HD 140297, HIP 76844) is a M3-type semiregular variable star located in the constellation Corona Borealis with a parallax of 2.93mas being a distance of . It varies between magnitudes 7.3 and 8.2 over 60.8 days. Located around 1228 light-years distant, it shines with a luminosity approximately 2180 times that of the Sun and has a surface temperature of 3309 K.
In 1907 it was announced that Williamina Fleming had discovered that the star, listed then as BD +39ð 2901, is a variable star. She had determined that from the examination of 26 photographic plates taken from 1892 to 1907. It was given its variable star designation, RR Coronae Borealis, in 1908.