Delmonico steak (alternately steak Delmonico) refers to a method of preparation from one of several cuts of beef (typically the Rib Cut) prepared Delmonico style, made by Delmonico's Restaurant in New York City during the mid-19th century.

There is controversy as to exactly which cut of steak was originally used by Delmonico's Restaurant. There are at least eight different cuts which are claimed to be the original for the Delmonico Steak. According to some sources, the original Delmonico steak was a boneless top sirloin, almost two inches thick with delicate marbling and cooked to the preference of the diner.

Delmonico's steak may now, in the 21st century, refer to other cuts, prepared differently in different parts of the USA. This wider variety of beef cuts may be broiled, fried, or grilled. Some of the steak cuts now commonly referred to as Delmonico steak include:

In addition to the steak, the original meal also included a potato dish, known as Delmonico's potatoes, prepared by making a mashed potato dish topped with grated cheese and buttered breadcrumbs, then baked until golden brown and served steaming.