main antagonist of J. K. Rowling's Harry Potter series
Lord Voldemort (, in the films; born Tom Marvolo Riddle) is a fictional character and the main antagonist in J. K. Rowling's series of Harry Potter novels. Voldemort first appeared in Harry Potter and the Philosopher's Stone, which was released in 1997. Voldemort appears either in person or in flashbacks in each book and its film adaptation in the series, except the third, Harry Potter and the Prisoner of Azkaban, where he is only mentioned.
Voldemort is the archenemy of Harry Potter, who according to a prophecy has "the power to vanquish the Dark Lord". Nearly every witch or wizard dares not utter his unmentionable name, and refers to him instead with such expressions as "You-Know-Who", "He Who Must Not Be Named" or "the Dark Lord". Voldemort's obsession with blood purity signifies his aim to rid the wizarding world of Muggle (non-magical) heritage and to conquer both worlds, Muggle and wizarding, to achieve pure-blood dominance. Through his mother's family, he is the last descendant of wizard Salazar Slytherin, one of the four founders of Hogwarts School of Witchcraft and Wizardry. He is the leader of the Death Eaters, a group of evil wizards and witches dedicated to ridding the Wizarding World of Muggles and establishing Voldemort as its supreme ruler.
Read more or edit on Wikipedia