Chateaubriand (French pronunciation: [ʃatobʁijɑ̃] ^ⓘ; sometimes called chateaubriand steak) is a dish that traditionally consists of a large front cut fillet of tenderloin grilled between two lesser pieces of meat that are discarded after cooking. While the term originally referred to the preparation of the dish, Auguste Escoffier named the specific front cut of the tenderloin the Chateaubriand.

In gastronomy of the 19th century, the steak for Chateaubriand could be cut from the sirloin, and served with a reduced sauce named Chateaubriand sauce or a similar, that was prepared with white wine and shallots moistened with demi-glace, and mixed with butter, tarragon, and lemon juice. It was also traditionally served with mushrooms.

Chateaubriand is named after the French author François-René de Chateaubriand.

There are several stories about what the original dish was. With French origins, the Larousse Gastronomique indicates that the dish Chateaubriand was created in 1822 by Montmireil, the personal chef of the Vicomte François-René de Chateaubriand who was at that time ambassador of France in the United Kingdom. Montmireil also created what was originally called pudding a la Chateaubriand but would eventually be called simply pudding diplomate. An alternative spelling of the Vicomte's surname is Châteaubriant, which term the Dictionnaire de l'Académie des Gastronomes gives as the source of the beef-cattle bred at the town of Châteaubriant, in Loire-Atlantique, France.

Originally the term itself was applied to the manner of preparation of the meat; however, by the 1870s at its introduction to the English, the term was transferred to the steak or cut of meat itself. Steak originally called filet de bœuf was now served as Chateaubriand. Montmireil originally roasted the Chateaubriand between two lesser cuts of meat. This technique enhanced both flavor and juiciness of the steak.

New York's Delmonico's Restaurant opened in 1827 as a pastry shop by Giovani and Pietro Delmonico but quickly expanded in 1830 to a full French restaurant. Louis Napoleon visited New York in 1837 and was a regular patron. Among the items on the first menu was "Beef tenderloin with sauce". In 1893, Charles Ranhofer, the former chef at Delmonico's Restaurant, described the exact cut of meat for his preparation method as being the center cuts of the beef tenderloin. This center loin is described by Ranhofer as having been given the name Chateaubriand. In this 1893 method, a twenty-ounce (pound and a quarter) tenderloin center is flattened to 3 centimetres (1.2 in) and broiled over a slow but steady fire for 16 minutes for exceptionally rare, 18 minutes for medium, and 20 minutes for well done. The finished steak is served with maître d'hôtel butter or gravy.

French chef Georges Auguste Escoffier gave names to different steak cuts. Tournedos was the name given for the kernels of the fillet, cut into rounds. Escoffier states:

Chateaubriands are obtained from the centre of the trimmed fillet of beef, cut two or three times the thickness of an ordinary fillet steak. However, when it is to be cooked by grilling the Chateaubriand should not be more than 500 g (1 lb 2 oz) in weight as, if larger than this, the outside tends to become too dry and hard before the inside is properly cooked. In modern practice though, Chateaubriands are served with any of the sauces and garnishes suitable for Tournedos and fillet steaks.