Gene Simmons (born Chaim Witz on August 25, 1949) is an American rock bassist, vocalist, and actor. He is best known as "The Demon", the blood-spitting, fire-breathing, and tongue-wagging bassist and one of the lead vocalists in the hard rock band Kiss, an act he co-founded in the early 1970s.

Simmons was born in Haifa, Israel in 1949, and emigrated to New York City at the age of eight, with his mother Florence Klein — a Jewish Hungarian immigrant. Florence and her brother, Larry Klein, were the only two members of her family to survive the Holocaust. His father, Feri Witz, did not accompany them to the U.S. After arriving in the U.S., young Chaim Witz took the name Eugene Klein (later Gene Klein), Klein being his mother's maiden name. In the late 1960s, he changed his name to Gene Simmons to honor legendary rockabilly performer Jumpin' Gene Simmons.

Simmons became involved with his first band, Lynx, then renamed The Missing Links, when he was a teenager. Eventually, he disbanded The Missing Links to form The Long Island Sounds, the name being a play on words relating to the estuary separating Long Island from Westchester County, New York, Connecticut and Rhode Island. While he played in these bands, he kept up odd jobs on the side to make more money, including making fanzines and trading used comic books. Simmons attended Sullivan County Community College in Loch Sheldrake, New York. He then joined a new band, Bullfrog Bheer, and the band recorded a demo, "Leeta"; this was later included on the Kiss box set.