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 of Johnny Lawrence in The Karate Kid (1984), The Karate Kid Part II (1986), and decades later reprises the role of Johnny in the Netflix series Cobra Kai (2018-), along with Ralph Macchio as Daniel.

During the 1980s, Zabka appeared in the comedy movies Just One of the Guys (1985) and Back to School (1986). Zabka also co-starred on the CBS television series The Equalizer as the son of the title character (1986–89). He also played Jack, Audrey's jock boyfriend, in National Lampoon's European Vacation (1985).