20th century

(19th century - 20th century - 21st century - more centuries)

Decades: 1900s 1910s 1920s 1930s 1940s 1950s 1960s 1970s 1980s 1990s

The 20th century lasted from 1901 to 2000 in the Gregorian calendar. Common usage sometimes regards it as lasting from 1900 to 1999, but this is considered incorrect due to the nonexistence of a "Year Zero" before AD 1. The 20th century is also sometimes known as the nineteen hundreds (1900s), referring to the latter usage. Decades are almost always considered as starting with the "0" year and named accordingly ("1960s", etc.), so the first decade of a century technically overlaps back into the preceding one.

However, a number of arguments have been used to justify the common usage. One was advanced by the scientist Stephen Jay Gould, that the first decade had only nine years. Another was that the astronomical year numbering system for years does have a year zero, the year normally known as 1 BC. In 2000 the International Organization for Standardization clarified ISO 8601 to use the astronomical year numbering system, so retrospectively endorsing all the people who had celebrated the new century a few months earlier.

The term is also used to describe various periods that overlap with the calendar definition most notably the Short twentieth century and the Modern period. It also had a place in popular culture shown by its use in names such as 20th Century Fox and the Twentieth Century Limited.



The twentieth century saw a remarkable shift in the way that vast numbers of people lived, as a result of technological, medical, social, ideological, and political innovations. Terms like ideology, world war, genocide, and nuclear war entered common usage, and became an influence on the lives of everyday people. War reached an unprecedented scale and level of sophistication, approximately 57 million people died as a result of the Second World War (1939-1945) alone. The trends of mechanization of goods and services and networks of global communication, which were begun in the 19th century, continued at an ever-increasing pace in the 20th. In spite of the terror and chaos, the 20th century saw many attempts at world peace. As the 35th President of the United States John F. Kennedy said:

What kind of peace do we seek? I am talking about a genuine peace, the kind of peace that makes life on earth worth living. Not merely peace in our time, but peace in all time. Our problems are man-made, therefore they can be solved by man. For in the final analysis, our most basic common link is that we all inhabit this small planet, we all breath the same air, we all cherish our children's future, and we are all mortal.

Virtually every aspect of life in virtually every human society changed in some fundamental way or another during the twentieth century.

For a more coherent overview of the historical events of the century, see The 20th century in review.

The 20th century has sometimes been called, both within and outside the United States, the American Century, though this is a controversial term.

Important developments, events and achievements

Science and technology

Wars and politics

  • Rising nationalism and increasing national awareness were among the causes of World War I, the first of two wars to involve all the major world powers including Germany, France, Italy, Japan, the United States and the British Commonwealth. World War I led to the creation of many new countries, especially in Eastern Europe.
  • The economic and political aftermath of World War I led to the rise of Fascism and Nazism in Europe, and shortly to World War II. This war also involved Asia and the Pacific, in the form of Japanese aggression against China and the United States. While the First World War mainly cost lives among soldiers, civilians suffered greatly in the Second -- from the bombing of cities on both sides, and in the unprecedented German genocide of the Jews and others, known as the Holocaust. Aftermath symptoms caused the Korean War, involving different countries, which Korea apart.
  • An Anglo-American covert operation named Operation Ajax (1953) overthrew the freely elected democratic Government of Iran and Iranian Prime Minister Mohammed Mossadegh. Excuses for the deposing included his nationalization of the oil industry which was previously operated by the Anglo-Iranian Oil Company. This event forms one of the root causes of the Middle-Eastern dislike of American policies and many events which surface today.
  • During World War I, in Russia the Bolshevik putsch led to the Russian Revolution (of October/November 1917). After the Soviet Union's involvement in World War II, Communism became a major force in global politics, spreading all over the world: notably, to Eastern Europe, China, Indochina and Cuba. This led to the Cold War and proxy wars with the western world, led by the United States.
  • The "fall of Communism" in the late 1980s freed Eastern and Central Europe from Soviet supremacy. It also led to the dissolution of the Soviet Union and Yugoslavia into successor states, many rife with ethnic nationalism.
  • Through the League of Nations and, after World War II, the United Nations, international cooperation increased. Other efforts included the formation of the European Union, leading to a common currency in much of Western Europe, the euro around the turn of the millennium.
  • The end of colonialism led to the independence of many African and Asian countries. During the Cold War, many of these aligned with the USA, the USSR, or China for defense.
  • The creation of Israel, a Jewish state in a mostly Arab region of the world, fueled many conflicts in the region, which were also influenced by the vast oil fields in many of the Arab countries.
  • Democratic nations finally began to extend voting privileges to all adults.
  • The Second Congo War starts in 1998 between several different nations
  • The Vietnam conflict was a major aspect of the 1960s and 1970s, and was the result of American attempts to suppress the spread of communism in south east asia.

Culture and entertainment

  • Movies, music and the media had a major influence on fashion and trends in all aspects of life. As many movies and music originate from the United States, American culture spread rapidly over the world.
  • After gaining political rights in the United States and much of Europe in the first part of the century, and with the advent of new birth control techniques women became more independent throughout the century.
  • Modern art developed new styles such as expressionism, cubism, and surrealism.
  • The automobile provided vastly increased transportation capabilities for the average member of Western societies in the early to mid-century, spreading even further later on. City design throughout most of the West became focused on transport via car. The car became a leading symbol of modern society, with styles of car suited to and symbolic of particular lifestyles.
  • Sports became an important part of society, becoming an activity not only for the privileged. Watching sports, later also on television, became a popular activity.

Disease and medicine

Natural resources and the environment

  • The widespread use of petroleum in industry -- both as a chemical precursor to plastics and as a fuel for the automobile and airplane -- led to the vital geopolitical importance of petroleum resources. The Middle East, home to many of the world's oil deposits, became a center of geopolitical and military tension throughout the latter half of the century.
  • A vast increase in fossil fuel consumption leads to depletion of natural resources, while air pollution possibly leads to global warming and the ozone hole. The problem is increased by world-wide deforestation, also causing a loss of biodiversity. The problem of a depletion of natural resources is decreased by advances in drilling technology which led to a net increase in the amount of fossil fuel that is readily obtainable at the end of the century, as compared with the amount considered obtainable at the beginning of the century.

Significant people

World leaders


Biology and Anthropology
Computer Science
Medicine and Pharmacy
Physics and Astronomy



Aerospace pioneers

Military leaders

Religious figures




Writers and poets

Sports figures

Decades and years


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