William Patrick Corgan, Jr. (born March 17, 1967 in Elk Grove Village, Illinois) is an American singer, songwriter, guitarist and occasional poet. Corgan is the vocalist and lead guitarist for alternative rock band The Smashing Pumpkins. When the band broke up in 2000, Corgan went on to form the short-lived Zwan with former Pumpkins drummer Jimmy Chamberlin. After releasing a solo album and a collection of poetry, Corgan reformed The Smashing Pumpkins with Chamberlin in 2006. Chamberlin departed the band in March 2009, leaving Corgan as the only original member.

Corgan is the oldest son of William Corgan Sr., a blues guitarist, and Martha Louise Maes Corgan Lutz. His parents had one more child, Ricky, before divorcing in 1970. William also fathered a half-brother, but Corgan has never found out who he is. His father was soon remarried to a flight attendant, and Corgan and his brother went to live with them in Glendale Heights, Illinois. During this time, Corgan alleges he was subject to much physical and emotional abuse by his stepmother. Corgan's half-brother, Jesse, was born in 1976. Jesse was afflicted with mild cerebral palsy, Tourette's syndrome, and other disabilities, and Corgan spent a good deal of his youth taking care of and defending him. The two remain close - Jesse joined The Smashing Pumpkins on stage in Chicago in December 2008. When Corgan's father and stepmother separated, all three children would live alone with the stepmother, with both of Corgan's birth parents living separately within an hour's drive.

Corgan, who grew much faster than his fellow students, was a strong athlete in elementary school. In addition to being a member of his Marquardt Middle School baseball team, he collected baseball cards (amassing over 10,000) and listened to every Chicago Cubs game. However, by the time he began attending Glenbard North High School in Carol Stream, Illinois, he had become only an average athlete. He decided to start playing guitar when he went over to a friend's house and saw his friend's Flying V. Corgan gave his savings to his father, who bought him a used imitation Gibson Les Paul. Corgan, Sr. steered his son stylistically, encouraging him to listen to Jeff Beck and Jimi Hendrix, but refused on-hand instruction because he was skeptical of his son's dedication. Billy Corgan would later claim he is a self-taught guitarist. His musical interests in his formative years included hard rock like Led Zeppelin, heavy metal pioneers Black Sabbath, and mainstream rock like Queen, Boston, ELO, and Cheap Trick. In high school, Corgan discovered alternative rock through Bauhaus, The Cure, and The Smiths.