Détente (/deɪˈtɑːnt/ ^ⓘ day-TAHNT, also UK: /ˈdeɪtɒnt/ DAY-tont; French for 'relaxation', French pronunciation: [detɑ̃t]) is the relaxation of strained relations, especially political ones, through verbal communication. The diplomacy term originates from around 1912, when France and Germany tried unsuccessfully to reduce tensions.

The term is often used to refer to a period of general easing of geopolitical tensions between the Soviet Union and the United States during the Cold War. Détente began in 1969 as a core element of the foreign policy of U.S. president Richard Nixon. In an effort to avoid an escalation of conflict with the Eastern Bloc, the Nixon administration promoted greater dialogue with the Soviet government in order to facilitate negotiations over arms control and other bilateral agreements. Détente was known in Russian as разрядка (razryadka), loosely meaning "relaxation of tension".

While the recognized era of détente formally began under the Richard Nixon presidency, there were prior instances of relationship relaxation between the United States and Soviet Union during the Cold War. Following the Cuban Missile Crisis in 1962, both the United States and Soviet Union agreed to install a direct hotline between Washington and Moscow, colloquially known as the red telephone. The hotline enabled leaders of both countries to communicate rapidly in the event of another potentially catastrophic confrontation.^{[citation needed]}

The period of détente in the Cold War saw the ratification of major disarmament treaties such as the Anti-Ballistic Missile Treaty and the creation of more symbolic pacts such as the Helsinki Accords. An ongoing debate among historians exists as to how successful the détente period was in achieving peace.

Détente is considered to have ended after the Soviet intervention in Afghanistan in 1979, which led to the U.S.' boycott of the 1980 Moscow Olympics. Ronald Reagan's election as president in 1980, based in large part on an anti-détente campaign, induced a period of rising tension. In his first press conference, Reagan claimed that the U.S.'s pursuit of détente had been used by the Soviet Union to further its interests.

Relations continued to increasingly sour through the unrest in Poland, the U.S.'s withdrawal from the SALT II arms treaty, and the NATO Able Archer exercise.

In response to the heightening tensions, U.S. secretary of state George P. Shultz shifted the Ronald Reagan administration's foreign policy towards another period of de-escalation with the Soviet Union especially following Mikhail Gorbachev coming to power. During Gorbachev's leadership, dialogue over the START arms reduction treaty meaningfully progressed. Diplomatic overtures were continued by the succeeding Bush administration, including the ratification of the START treaty, up until the collapse of the Soviet Union in 1991. This period of a renewed de-escalation from 1984 to 1991 is sometimes referred to as the second period of détente.

According to Eric Grynaviski, "Soviet and U.S. decision-makers had two very different understandings about what détente meant" while simultaneously holding "an inaccurate belief that both sides shared principles and expectations for future behaviour."