Jonathan Anthony Wisniski (September 20, 1951) better known as Greg "The Hammer" Valentine, a American professional wrestler, He is the son of wrestler Johnny Valentine.
In the course of his career, which has spanned over four decades, Valentine has held more than 40 championships, including the NWA United States Heavyweight Championship, WWF Intercontinental Heavyweight Championship and WWF World Tag Team Championship. An alumnus of Mid-Atlantic Championship Wrestling, the World Wrestling Federation and World Championship Wrestling, he was inducted into the WWE Hall of Fame class of 2004 and the Professional Wrestling Hall of Fame in 2016.