Solidarity (Polish: „Solidarność”, pronounced [sɔliˈdarnɔɕt͡ɕ] ^ⓘ), full name Independent Self-Governing Trade Union "Solidarity" (Niezależny Samorządny Związek Zawodowy „Solidarność” [ɲɛzaˈlɛʐnɨ samɔˈʐɔndnɨ ˈzvjɔ̃zɛɡ zavɔˈdɔvɨ sɔliˈdarnɔɕt͡ɕ], abbreviated NSZZ „Solidarność”), is a Polish trade union founded in August 1980 at the Lenin Shipyard in Gdańsk, Poland. Subsequently, it was the first independent trade union in a Warsaw Pact country to be recognised by the state.

The union's membership peaked at 10 million in September 1981, representing one-third of the country's working-age population. In 1983 Solidarity's leader Lech Wałęsa was awarded the Nobel Peace Prize, and the union is widely recognized as having played a central role in the end of communist rule in Poland. This led to the appointment of the first noncommunist Prime Minister since the 1940s.

In the 1980s, Solidarity was a broad anti-authoritarian social movement, using methods of civil resistance to advance the causes of workers' rights and social change. The Government attempted in the early 1980s to destroy the union through the imposition of martial law in Poland and the use of political repression.

Operating underground, with substantial financial support from the Vatican and the United States, the union survived and in the late 1980s had entered into negotiations with the government.

The 1989 round table talks between the government and the Solidarity-led opposition produced an agreement for the 1989 legislative elections, the country's first pluralistic election since 1947. By the end of August, a Solidarity-led coalition government was formed, and in December 1990 Wałęsa was elected President of Poland.

Following Poland's transition to liberal capitalism in the 1990s and the extensive privatization of state assets, Solidarity's membership declined substantially. By 2010, 30 years after its founding, the union had lost more than 90% of its original membership.

In the 1970s Poland's government raised food prices while wages were stagnant. This and other stresses led to protests in 1976 and a subsequent government crackdown on dissent. The KOR, the ROPCIO and other groups began to form underground networks to monitor and oppose the government's behaviour. Labour unions formed an important part of this network. In 1979, the Polish economy shrank for the first time since World War II, by two percent. Foreign debt reached around $18 billion by 1980.

Anna Walentynowicz was fired from the Gdańsk Shipyard on 7 August 1980, five months before she was due to retire, for participation in the illegal trade union. This management decision enraged the workers of the shipyard, who staged a strike action on 14 August, defending Walentynowicz and demanding her reinstatement. She and Alina Pienkowska transformed a strike over bread and butter issues into a solidarity strike in sympathy with strikes on other establishments.