Regulus Black is a fictional character from the Harry Potter series created by J.K. Rowling. He is the younger brother of Sirius Black and a member of the pure-blood Black family. Regulus was initially a loyal follower of Lord Voldemort but later became disillusioned with the dark wizard's methods and the consequences of his actions. In the series, Regulus is known for his bravery and moral awakening. He played a crucial role in the story by stealing one of Voldemort's Horcruxes, which ultimately contributed to the dark wizard's defeat. His character highlights themes of redemption and the struggle between good and evil.