Contemporary history, in English-language historiography, is a subset of modern history that describes the historical period from about 1945 to the present. In the social sciences, contemporary history is also continuous with, and related to, the rise of postmodernity.

Contemporary history is politically dominated by the Cold War (1947–1991) between the Western Bloc, led by the United States, and the Eastern Bloc, led by the Soviet Union. The confrontation spurred fears of a nuclear war. An all-out "hot" war was avoided, but both sides intervened in the internal politics of smaller nations in their bid for global influence and via proxy wars. The Cold War ultimately ended with the Revolutions of 1989 and the dissolution of the Soviet Union in 1991. The latter stages and aftermath of the Cold War enabled the democratization of much of Europe, Africa, and Latin America. Decolonization was another important trend in Southeast Asia, the Middle East, and Africa as new states gained independence from European colonial empires during the period from 1945–1975. The Middle East also saw a conflict involving the new state of Israel, the rise of petroleum politics, the continuing prominence but later decline of Arab nationalism, and the growth of Islamism. The first supranational organizations of government, such as the United Nations and European Union, emerged during the period after 1945.

Countercultures rose and the sexual revolution transformed social relations in western countries between the 1960s and 1980s, as seen in the protests of 1968. Living standards rose sharply across the developed world because of the post-war economic boom. Japan and West Germany both emerged as exceptionally strong economies. The culture of the United States spread widely, with American television and movies spreading across the world. Some Western countries began a slow process of deindustrializing in the 1970s; globalization led to the emergence of new financial and industrial centers in Asia. The Japanese economic miracle was later followed by the Four Asian Tigers of Hong Kong, Singapore, South Korea and Taiwan. China launched major economic reforms from 1979 onward, becoming a major exporter of consumer goods around the world.

Science made new advances after 1945, which included spaceflight, nuclear technology, lasers, semiconductors, molecular biology, genetics, particle physics, and the Standard Model of quantum field theory. The first commercial computers were created, followed by the Internet, beginning the Information Age.

In 1945, the Allies of World War II had defeated all significant opposition to them. They established the United Nations to govern international relations and disputes. A looming question was how to handle the defeated Axis nations and the shattered nations that the Axis had conquered. Following the Yalta Conference, territory was divided into zones for which Allied country would have responsibility and manage rebuilding. While these zones were theoretically temporary (such as the eventual fate of occupied Austria, which was released to independence as a neutral country), growing tensions between the Western Bloc, led by the United States, with the Eastern Bloc, led by the Soviet Union, meant that many calcified into place. Countries in Soviet zones of Eastern Europe had communist regimes installed as satellite states. The Berlin Blockade of 1948 led to a Western Airlift to preserve West Berlin and signified a cooling of East-West relations. Germany split into two countries in 1949, liberal-democratic West Germany and communist East Germany. The conflict as a whole would become known as the Cold War. The Western Bloc formed NATO in 1949 while the Eastern Bloc formed the Warsaw Pact in 1955. Direct combat between the new Great Powers was generally avoided, although proxy wars fought in other countries by factions equipped by one side against the other side's faction occurred. An arms race to develop and build nuclear weapons happened as policymakers wanted to ensure their side had more if it came to a war.

In East Asia, Chiang Kai-shek's Republic of China was overthrown in the Chinese Communist Revolution from 1945–1949. His government retreated to Taiwan, but both the nationalist KMT government and the new communist mainland government under Mao Zedong continued to claim authority over all of China. Korea was divided similarly to Germany, with the Soviet Union occupying the North and the United States occupying the South (future North Korea and South Korea). Unlike Germany, the conflict there turned hot, as the Korean War erupted from 1950–1953. Korea was not reunified under either government, however, due to strong support from both the US and China for their favored side; it became a frozen conflict instead. Japan was given a new constitution foreswearing aggressive war in 1947, and the American occupation ended in 1952, although a treaty of mutual aid with the US was soon signed. The US also granted the Philippines their independence in 1946 while keeping close relations.

The Middle East became a hotbed of instability. The new Jewish state of Israel declared its independence, recognized by both the United States and the Soviet Union, after which followed the 1948 Arab–Israeli War. Egypt's weak and ineffective king Farouk was overthrown in the 1952 Egyptian revolution, and replaced by General Nasser; the 1953 Iran coup saw the American-friendly shah Mohammad Reza Pahlavi remove the democratic constraints on his government and take power directly; and Iraq's Western-friendly monarchy was overthrown in 1958. Nasser's Egypt would go on to face the Suez Crisis in 1956, briefly unify with Syria as the United Arab Republic (UAR) from 1958 to 1961, and expensively intervene in the North Yemen civil war from 1962 to 1970.

Decolonization was the most important development across Southeast Asia and Africa from 1946–1975, as the old British, French, Dutch, and Portuguese colonial empires were dismantled. Many new states were given their independence, but soon found themselves having to choose between allying with the Western Bloc, Eastern Bloc, or attempting to stay neutral as a member of the Non-Aligned Movement. British India was granted independence in 1947 without an outright war of independence being required. It was partitioned into Hindu-majority India and Muslim-majority Pakistan (West Pakistan and East Pakistan, future Pakistan and Bangladesh); Indo-Pakistani wars were fought in 1947, 1965, and 1971. Sukarno took control of an independent Indonesia in 1950, as attempts to reinstate Dutch rule in 1945–1949 had largely failed, and took an independent-to-Eastern leaning stance. He would later be overthrown by Suharto in 1968, who took a pro-Western stance. The Federation of Malaya was granted independence in 1957, with the concurrent fighting of the Malayan Emergency against communist forces from 1948–1960. The French unsuccessfully fought the First Indochina War in an attempt to hold on to French Indochina; at the 1954 Geneva Conference, the new states of Cambodia, Laos, the Democratic Republic of Vietnam, and the eventual Republic of Vietnam were created. The division of Indochina eventually led to the Vietnam War in the 1960s and 70s (as well as the Laotian Civil War and Cambodian Civil War), which ended in communist North Vietnam unifying the country in 1975.