The Yamato-class battleships (大和型戦艦, Yamato-gata senkan) were two battleships of the Imperial Japanese Navy, Yamato and Musashi. Their keels were laid down in 1937 and 1938, and they were commissioned as designed in 1941 and 1942. A third hull, laid down in 1940, was converted to the aircraft carrier Shinano during construction. Two further ships were planned but never constructed.

Displacing nearly 72,000 long tons (73,000 t) at full load, the completed battleships were the heaviest ever constructed. The class carried the largest naval artillery ever fitted to a warship, nine 460 mm (18.1 in) naval guns, each capable of firing 1,460 kg (3,220 lb) shells over 42 km (26 mi).

Because of the threat of U.S. submarines and aircraft carriers, Yamato and Musashi spent the majority of their careers in naval bases at Brunei, Truk, and Kure—deploying on several occasions in response to U.S. raids on Japanese bases.

All three ships were sunk by the U.S. Navy; Musashi by air strikes while participating in the Battle of Leyte Gulf in October 1944, Shinano after being torpedoed by the submarine USS Archerfish while under way from Yokosuka to Kure for fitting out in November 1944, and Yamato by air strikes while en route from Japan to Okinawa as part of Operation Ten-Go in April 1945.

The design of the Yamato-class battleships was shaped by expansionist movements within the Japanese government, Japanese industrial power, and the need for a fleet powerful enough to intimidate likely adversaries. Most importantly, the latter, in the form of the Kantai Kessen or Decisive Battle Doctrine, a naval strategy adopted by the Imperial Japanese Navy prior to the Second World War, in which the Japanese navy would win a war by fighting and winning a single, decisive naval action.

After the end of the First World War, many navies—including those of the United States, the United Kingdom, and Imperial Japan—continued and expanded construction programs that had begun during the conflict. The enormous costs associated with these programs pressured their government leaders to begin a disarmament conference. On 8 July 1921, the United States' Secretary of State Charles Evans Hughes invited delegations from the other major maritime powers—France, Italy, Japan, and the United Kingdom—to come to Washington, D.C., and discuss a possible end to the naval arms race. The subsequent Washington Naval Conference resulted in the Washington Naval Treaty. Along with many other provisions, it limited all future battleships to a standard displacement of 35,000 long tons (35,562 t; 39,200 short tons) and a maximum gun caliber of 16 inches (406 mm). It also agreed that the five countries would not construct more capital ships for ten years and would not replace any ship that survived the treaty until it was at least twenty years old.

In the 1930s, the Japanese government began a shift towards ultranationalist militancy. This movement called for the expansion of the Empire of Japan to include much of the Pacific Ocean and Southeast Asia. The maintenance of such an empire—spanning 3,000 miles (4,800 km) from China to Midway Island—required a sizable fleet capable of sustained control of territory. Although all of Japan's battleships built prior to the Yamato class had been completed before 1921—as the Washington Treaty had prevented any more from being completed—all had been either reconstructed or significantly modernized, or both, in the 1930s. This modernization included, among other things, additional speed and firepower, which the Japanese intended to use to conquer and defend their aspired-to empire. When Japan withdrew from the League of Nations in 1934 over the Mukden Incident, it also renounced all treaty obligations, freeing it to build warships larger than those of the other major maritime powers.

Japan's intention to acquire resource-producing colonies in the Pacific and Southeast Asia would likely lead to confrontation with the United States; thus the U.S. became Japan's primary potential enemy. The U.S. possessed significantly greater industrial power than Japan, with 32.2% of worldwide industrial production compared to Japan's 3.5%. Furthermore, several leading members of the United States Congress had pledged "to outbuild Japan three to one in a naval race". Consequently, as Japanese industrial output could not compete with American industrial power, Japanese ship designers developed plans for new battleships individually superior to their counterparts in the United States Navy. Each of these battleships would be capable of engaging multiple enemy capital ships simultaneously, eliminating the need to expend as much industrial effort as the U.S. on battleship construction.