What is the name of the sandwich McDonald's introduced in 1971 to compete with the Whopper?

The sandwich McDonald's introduced in 1971 to compete with the Whopper was the Quarter Pounder.

The Quarter Pounder was created by Al Bernardin, a McDonald's franchisee and former company vice president of product development. He introduced it at his restaurants in Fremont, California, in 1971, using a larger beef patty to appeal to customers who wanted a more substantial burger.

The burger's name refers to the patty's approximate pre-cooked weight: one quarter of a pound, or four ounces. Bernardin's local launch succeeded, and McDonald's added the Quarter Pounder to its national American menu in 1973. Its larger patty positioned it as a direct competitor to Burger King's Whopper.

The Quarter Pounder is often confused with the Big Mac because both are signature McDonald's sandwiches. The Big Mac, however, is defined by its two smaller patties and distinctive middle bun. In metric-market countries, the Quarter Pounder may use another name, such as the Royal, because pounds are not the usual measurement.