The patty melt is variously described as a variant of the traditional American cheeseburger, topped with fried onions and served on sliced bread instead of a traditional bun, or as a variant of a grilled cheese that includes a hamburger patty and fried onions.

[1][2][3] The sandwich consists of a ground beef patty topped with melted cheese (traditionally Swiss cheese) and usually with caramelized onions between two slices of griddled bread (typically caraway-seeded rye or marbled rye, though sourdough or Texas toast are sometimes substituted in some regions, including the Southern U.S.)[1][4] It is typically made without condiments or garnishes.

[6] It is unclear when the patty melt was invented, but it was most likely the mid-20th century, either during the Great Depression or the postwar economic boom.

[6] According to New York Times food writer Pete Wells in 2024, the sandwich is "virtually unknown" outside of the United States; Wells theorizes that the amount of space on a flattop grill required to grill onions, patty, and bread at the same time has restricted its appeal outside of typical short-order restaurants.

[1] It is typically on the menu of diners, coffee shops, and lunch counters, but in the early 2020s it started to appear on some upscale menus.