The Big King sandwich is one of the major hamburger products sold by the international fast-food restaurant chain Burger King, and was part of its menu for more than twenty years. As of March 2019, it is sold in the United States under its 1997 Big King XL formulation. During its testing phase in 1996–1997, it was originally called the Double Supreme and was configured similarly to the McDonald's Big Mac—including a three-piece roll. It was later reformulated as a more standard double burger during the latter part of product testing in 1997. It was given its current name when the product was formally introduced in September 1997, but maintained the more conventional double cheeseburger format.
The product was renamed King Supreme in 2001 when it was slightly reformulated as part of a menu restructuring during a period of corporate decline. A later restructuring eliminated the King Supreme in favor of its new BK Stacker line of sandwiches. When the Stacker line was discontinued in the United States shortly after, the Big King returned in November 2013 as a permanent product.
Despite being off the menu in the United States for several years, the product was still sold in several other countries under several names during the interim of its unavailability in the United States. One such example sold by BK's European arm of the company is a larger version of the sandwich called the Big King XXL, based on the company's Whopper sandwich. The Big King XXL is part of a line of larger double cheeseburgers known as the BK XXL line; the XXL line was the center of controversy over product health standards and advertising in Spain when first introduced.
There was a chicken variant of the sandwich in the United States and Canada. To promote continuing interest in the product, Burger King occasionally releases limited-time variants on the Big King.
The burger was introduced by Hungry Jack's Australia in 2020 under the name Big Jack, with a slightly altered recipe and controversial advertising campaign that highlighted its similarity to the Big Mac, leading to a trademark infringement lawsuit being filed by McDonalds. The larger version was called "Mega Jack".