Bill Kaulitz (born 1 September 1989), also known as Billy for his solo project, is a German singer and songwriter. He is best known for his work as the lead vocalist of the pop rock band Tokio Hotel.

Kaulitz was born on 1 September 1989 in Leipzig, East Germany. He has an identical twin brother, Tom, who is older by ten minutes. His parents, Simone Kaulitz and Jörg W.