Rev-Erb beta (Rev-Erbβ), also known as nuclear receptor subfamily 1 group D member 2 (NR1D2), is a member of the Rev-Erb protein family. Rev-Erbβ, like Rev-Erbα, belongs to the nuclear receptor superfamily of transcription factors and can modulate gene expression through binding to gene promoters. Together with Rev-Erbα, Rev-Erbβ functions as a major regulator of the circadian clock. These two proteins are partially redundant. Current research suggests that Rev-Erbβ is less important in maintaining the circadian clock than Rev-Erbα; knock-out studies of Rev-Erbα result in significant circadian disruption but the same has not been found with Rev-Erbβ. Rev-Erbβ compensation for Rev-Erbα varies across tissues, and further research is needed to elucidate the separate role of Rev-Erbβ.