A hamburger, or simply burger, is a food consisting of fillings —usually a patty of ground meat, typically beef—placed inside a sliced bun or bread roll. Hamburgers are often served with cheese, lettuce, tomato, onion, pickles, bacon, or chilis; condiments such as ketchup, mustard, mayonnaise, relish, or a “special sauce”, often a variation of Thousand Island dressing; and are frequently placed on sesame seed buns. A hamburger topped with cheese is called a cheeseburger.

The term burger can also be applied to the meat patty on its own, especially in the United Kingdom, where the term patty is rarely used, or the term can even refer simply to ground beef. Since the term hamburger usually implies beef, for clarity burger may be prefixed with the type of meat or meat substitute used, as in beef burger, turkey burger, bison burger, portobello burger, or veggie burger. In Australia and New Zealand, a piece of chicken breast on a bun is known as a chicken burger, which would generally not be considered to be a burger in the United States; where it would generally be called a chicken sandwich, but in Australian English and New Zealand English a sandwich requires sliced bread (not a bun), so it would not be considered a sandwich.

Hamburgers are typically sold at fast-food restaurants, diners, and specialty and high-end restaurants. There are many international and regional variations of hamburgers.

The origin of the hamburger is unclear, though “hamburger steak sandwiches” have been advertised in U.S. newspapers from New York to Hawaii since at least the 1890s. The invention of hamburgers is commonly attributed to various people, including Charlie Nagreen, Frank and Charles Menches, Oscar Weber Bilby, Fletcher Davis, or Louis Lassen. White Castle traces the origin of the hamburger to Hamburg, Germany with its invention by Otto Kuase. Some have pointed to a recipe for “Hamburgh sausages” on toasted bread, which was published in The Art of Cookery Made Plain and Easy by Hannah Glasse in 1747. Hamburgers gained national recognition in the U.S. at the 1904 St. Louis World’s Fair when the New York Tribune referred to the hamburger as “the innovation of a food vendor on the pike”. No conclusive argument has ended the dispute over invention. An article from ABC News sums up: “One problem is that there is little written history. Another issue is that the spread of the burger happened largely at the World’s Fair, from tiny vendors that came and went in an instant. And it is entirely possible that more than one person came up with the idea at the same time in different parts of the country.”

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