Justin Hammer is a fictional character in the Marvel Comics universe, primarily known as a businessman and industrialist. He is often portrayed as a rival to Tony Stark, the genius behind Iron Man. Hammer is the head of Hammer Industries, a company that specializes in weapons manufacturing and technology. In the Marvel Cinematic Universe, Justin Hammer is depicted by actor Sam Rockwell in the film Iron Man 2. He is characterized by his ambition and desire to outshine Stark, often resorting to unethical practices to achieve his goals. Hammer's character serves as a representation of corporate greed and competition in the tech industry.