The Fleet Problems were a series of United States Navy exercises conducted in the interwar period, later resurrected by the United States Pacific Fleet around 2016.

The first twenty-one Fleet Problems — labeled by Navy leadership as Fleet Problem I through Fleet Problem XXI — were conducted between 1923 and 1940. The culmination of the Navy's annual training maneuvers, they were unscripted, free play exercises involving large concentrations of ships, airplanes, and troops. Fleet Problem XXII, scheduled for 1941, was canceled because of rising tensions with Japan on the eve of the US's entry into World War II. Following the outbreak of war, Fleet Problems underwent a prolonged hiatus, with other names being used to describe large American naval exercises. However, the term was revived in the 21st century under Admiral Scott H. Swift, with Fleet Problem XXIII through XXVIII taking place in the Pacific from 2016 on. Since 2018, the US Navy has not publicly used the historical roman numeral numbering scheme.

The Fleet problems of the 1920's and 1930's were an evolutionary step from existing fleet training exercises. In the 1870's and 1880's, the US Navy was heavily influenced by a reform movement, championed by progressive officers like Admiral William Sims, Admiral Stephen Luce, and Alfred Thayer Mahan. This generation of reform-oriented officers sought to grow the US Navy into a credible battle fleet, which required improving the Navy's equipment, personnel, and training. This movement prompted the creation of the United States Naval Institute in 1873 and the Naval War College in 1884, which both became intellectual hubs for further reform. Modern shipbuilding began in 1882, replacing the largely decrepit wooden-hulled ships built during and after the Civil War with new, steel-hulled vessels, beginning with USS Dolphin. Finally, after the number of modern warships increased throughout the 1880s, large-scale fleet exercises began in 1889. Large-scale exercises continued on a regular basis until the United States entered World War I in 1917. The US Navy again held a large exercise in 1921, but remained administratively divided into Pacific and Atlantic Fleets until the creation of the United States Fleet in 1922. This large concentration of peacetime forces under a unified staff and commander (a position known as the Commander-in-Chief, US Fleet, or CINCUS), Admiral Hilary P. Jones, set the stage for the mass exercises that would become known as fleet problems.

From their first announcement, the fleet problems were national news. On 25 December 1922, the New York Times reported about the upcoming exercises for the first time, proclaiming that "all eighteen of the battleships which the United States Government is permitted to retain by the five-power naval treaty will be engaged in these manoeuvres, representing an aggregate of 500,650 tons."

Fleet Problem I was held off the coast of Panama in February and March 1923. 165 ships and nearly 40,000 men, sailing from both coasts of the United States, participated in the exercise. The United States Battle Fleet, which constituted the attacking Black force, was tasked with attacking the Panama Canal. Shortly after the ships of the United States Scouting Fleet—which, playing the Blue Force, was tasked to defend the Panama Canal—the canal into the Pacific, Black Force launched a simulated air raid. Two battleships, USS New York (BB-34) and USS Oklahoma (BB-37) simulated aircraft carriers modeled after the under-construction USS Langley (CV-1). A single plane launched from Oklahoma—representing a 15-plane squadron—dropped 10 miniature bombs and theoretically "destroyed" the spillway of the Gatun Dam. This trapped the ships of the defending Blue Force in the Gulf of Panama, and allowed the Black Force to make a unopposed surface attack on the coast, ending the fleet problem. The exercise ended with a gunnery exercise, with the fleet sinking the pre-dreadnought battleship USS Iowa. Fleet Problem I was widely regarded as a success, including by members of Congress and reporters who had observed the fleets in action, setting the stage for a repeated experimentation in future years.

Fleet Problems II, III, and IV all represented different phases of the same scenario, exploring the initial moves in a notional war against Japan, and took place within the same two months of 1924. These exercises allowed the Army and Navy to validate and practice portions of War Plan Orange, the operations plan for a hypothetical war against Japan in the Pacific, which was formally adopted by the Joint Army and Navy Board later that year.

Fleet Problem II, which ran from 2 to 15 January, followed the movement of the Battle Fleet, designated as the "Blue Force", from its base on the West Coast to Panama. This was designed to simulate the first leg of an advance from Hawaii towards Asia, especially how well the ships could handle the long transoceanic voyage. During Fleet Problem II, the Navy refined at sea refueling techniques, including refueling side-by-side for the first time between the oiler Cuyama (AO-3) and three other ships.

During Fleet Problem III, the Scouting Force, designated the "Black Force," transited from its homeport in the Chesapeake Bay towards the Panama Canal from the Caribbean side. Once in the Caribbean, the naval forces involved in Fleet Problem III joined with the 15th Naval District and the Army's Panama Division in a larger joint exercise. The Blue force defended the canal from an attack from the Caribbean by the Black force, operating from an advance base in the Azores. This portion of the exercise also aimed to practice amphibious landing techniques and transiting a fleet rapidly through the Panama Canal from the Pacific side.