The Whopper is the signature hamburger and an associated product line sold by international fast food restaurant chain Burger King and its Australian franchise Hungry Jack's. Introduced in 1957, the hamburger has undergone several reformulations such as portion resizing and bread changes. The hamburger is well known in the fast food industry, with Burger King billing itself as "the Home of the Whopper" in its advertising, signage, and in its concept store, the BK Whopper Bar. Due to its position in the marketplace, the Whopper has prompted Burger King's competitors to try to develop similar products designed to compete against it.