William Michael "Billy" Zabka (born October 20, 1965) is an American actor, martial artist, screenwriter, and film producer. Zabka is best known for his role as Johnny Lawrence in the films The Karate Kid (1984) and The Karate Kid Part II (1986), and decades later he reprised the role of Johnny in the Netflix series Cobra Kai (2018–), in which he starred alongside Ralph Macchio as Daniel.

In the 1980s, Zabka appeared in the comedy films Just One of the Guys (1985) and Back to School (1986). Zabka also played the son of the main character in the CBS television series The Equalizer (1986–89). He also played Jack, Audrey's athlete boyfriend, in National Lampoon's European Vacation (1985).

In the 1990s and 2000s, he appeared mainly in independent films while studying filmmaking. In 2003 he wrote and produced the short film The Bridge, shot on location in the Czech Republic and Poland. The Bridge (also known as The Bridge) premiered at the Sundance Film Festival in 2003 and received numerous awards at prestigious film festivals, including the Best of Festival award at the Palm Springs International Short Film Festival in 2003. In 2004 he was nominated for an Academy Award for The Bridge in the category Best Live Action Short Film.