Solidarity (Polish: Solidarność, pronounced [sɔliˈdarnɔɕt͡ɕ] (listen)), full name Independent Self-Governing Trade Union "Solidarity" (Niezależny Samorządny Związek Zawodowy „Solidarność”, abbreviated NSZZ „Solidarność” [ɲɛzaˈlɛʐnɨ samɔˈʐɔndnɨ ˈzvjɔ̃zɛɡ zavɔˈdɔvɨ sɔliˈdarnɔɕt͡ɕ]), 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. Solidarity's leader Lech Wałęsa was awarded the Nobel Peace Prize in 1983 and the union is widely recognised as having played a central role in the end of Communist rule in Poland.

In the 1980s, Solidarity was a broad anti-bureaucratic social movement, using methods of civil resistance to advance the causes of workers' rights and social change. Government attempts in the early 1980s to destroy the union through the imposition of martial law in Poland and the use of political repression failed. Operating underground, with significant financial support from the Vatican and the United States, the union survived and by the later 1980s had entered into negotiations with the government.

The 1989 round table talks between the government and the Solidarity-led opposition produced 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 privatisation of state assets, Solidarity's membership declined significantly; by 2010, 30 years after being founded, the union had lost more than 90% of its original membership.