By 14 B.C., western Hungary was part of the Roman Empire's provinces of Pannonia and Dacia. The area east of the Danube was never a part of the Roman Empire and was largely occupied by various Germanic and Asiatic peoples. In 896 all of Hungary was invaded by the Magyars, who founded a kingdom. Christianity was accepted during the reign of Stephen I (Saint Stephen), 977–1038. A devastating invasion by the Mongols killed half of Hungary's population in 1241. The peak of Hungary's great period of medieval power came during the reign of Louis I the Great (1342–1382), whose dominions touched the Baltic, Black, and Mediterranean seas. War with the Turks broke out in 1389, and for more than 100 years the Turks advanced through the Balkans. When the Turks smashed a Hungarian army in 1526, western and northern Hungary accepted Hapsburg rule to escape Turkish occupation. Transylvania became independent under Hungarian princes. Intermittent war with the Turks was waged until a peace treaty was signed in 1699.

After the suppression of the 1848 revolt, led by Louis Kossuth, against Hapsburg rule, the dual monarchy of Austria-Hungary was set up in 1867. The dual monarchy was defeated with the other Central Powers in World War I. After a short-lived republic in 1918, the chaotic Communist rule of 1919 under Béla Kun ended with the Romanians occupying Budapest on Aug. 4, 1919. When the Romanians left, Adm. Nicholas Horthy entered the capital with a national army. The Treaty of Trianon of June 4, 1920, by which the Allies parceled out Hungarian territories, cost Hungary 68% of its land and 58% of its population.

In World War II, Hungary allied with Germany, which aided the country in recovering lost territories. Following the German invasion of Russia on June 22, 1941, Hungary joined the attack against the Soviet Union, but withdrew in defeat from the eastern front by May 1943. Germany occupied the country for the remainder of the war and set up a puppet government. Hungarian Jews and gypsies were sent to death camps. The German regime was driven out by the Soviets in 1944–1945.

By the Treaty of Paris (1947), Hungary had to give up all territory it had acquired since 1937 and to pay $300 million reparations to the USSR, Czechoslovakia, and Yugoslavia. In 1948, the Communist Party, with the support of Soviet troops, seized control. Hungary was proclaimed a People's Republic and one-party state in 1949. Industry was nationalized, the land collectivized into state farms, and the opposition terrorized by the secret police. The terror, modeled after that of the USSR, reached its height with the trial and life imprisonment of József Cardinal Mindszenty, the leader of Hungary's Roman Catholics, in 1948. On Oct. 23, 1956, an anti-Communist revolution broke out in Budapest. To cope with it, the Communists set up a coalition government and called former premier Imre Nagy back to head the government. But he and most of his ministers sympathized with the anti-Communist opposition, and he declared Hungary a neutral power, withdrawing from the Warsaw Treaty and appealing to the United Nations for help. One of his ministers, János Kádár, established a counterregime and asked the USSR to send in military power. Soviet troops and tanks suppressed the revolution in bloody fighting after 190,000 people had fled the country. Under Kádár (1956–1988), Communist Hungary maintained more liberal policies in the economic and cultural spheres, and Hungary became the most liberal of the Soviet-bloc nations of eastern Europe. Continuing his program of national reconciliation, Kádár emptied prisons, reformed the secret police, and eased travel restrictions.

In 1989, Hungary's Communists abandoned their monopoly on power voluntarily, and the constitution was amended in Oct. 1989 to allow for a multiparty state. The last Soviet troops left Hungary in June 1991, thereby ending almost 47 years of military presence. The transition to a market economy proved difficult. In April 1999, Hungary became part of NATO, and in May 2004, it joined the EU