Adam Michnik (Polish: [ˈadam ˈmixɲik]; born 17 October 1946) is a Polish historian, essayist, former dissident, public intellectual, as well as co-founder and editor-in-chief of the Polish newspaper Gazeta Wyborcza.

Reared in a family of committed communists, Michnik became an opponent of Poland's communist regime at the time of the party's anti-Jewish purges of 1968. He was imprisoned after the 1968 March Events and again after the imposition of martial law in 1981. He has been called "one of Poland's most famous political prisoners".

Michnik played a crucial role during the Polish Round Table Talks, as a result of which the communists agreed to call elections in 1989, which were won by Solidarity. Though he has withdrawn from active politics, he has "maintained an influential voice through journalism". He has received many awards and honors, including the Legion of Honour and European of the Year. He is also one of the 25 leading figures on the Information and Democracy Commission launched by Reporters Without Borders. In 2022, he received the Princess of Asturias Award in the category "Communication and Humanities".

Adam Michnik was born in Warsaw, Poland, to a family of communist activists of Jewish origin. His father Ozjasz Szechter was First Secretary of the Communist Party of Western Ukraine, and his mother Helena Michnik was a historian, communist activist, and children's-book author. His step-brother on his mother's side, Stefan Michnik, was a military judge in the 1950s, who passed sentences, including executions, in politically motivated trials of members of Polish anti-Nazi resistance fighters. Stefan Michnik (who lived in Sweden from 1968 until his death in 2021), was later formally accused of zbrodnie komunistyczne ("communist crimes") by the Polish Institute of National Remembrance.

A step-brother of Adam Michnik on his father's side, Jerzy Michnik (born 1929), settled in Israel after 1957 and then moved to New York.

While attending primary school, he was an active member of the Polish Scouting Association (ZHP), in a troop which was led by Jacek Kuroń. During secondary school, this particular Scouting troop was banned, and Adam began to participate in meetings of the Crooked Circle Club. After its closing in 1962, with the encouragement from Jan Józef Lipski and under Adam Schaff's protection, he founded a discussion group, "Contradiction Hunters Club" (Klub Poszukiwaczy Sprzeczności); he was one and the most visible leader of the left wing student opposition group, the Komandosi.

In 1964, he began to study history at Warsaw University. A year later he was suspended because he disseminated an open letter to the members of Polish United Workers' Party (PZPR) among his schoolmates. Its authors, Jacek Kuroń and Karol Modzelewski appealed for a beginning of reforms which would repair the political system in Poland. In 1965, the PZPR forbade the printing of his works. In 1966, he was suspended for the second time for organizing a discussion meeting with Leszek Kołakowski, who was expelled from the PZPR several weeks earlier, for criticizing its leaders. From then on, he wrote under a pseudonym to several newspapers including "Życie Gospodarcze", "Więź", and "Literatura".

In March 1968, he was expelled from the university for his activities during 1968 Polish political crisis. The crisis was ignited by the ban of Kazimierz Dejmek's adaptation of Adam Mickiewicz's poetic drama Dziady ("Forefathers' Eve") in the National Theatre. The play contained many anti-Russian allusions, which were greeted with enthusiastic applause by the audience. Michnik and another student, Henryk Szlajfer, recounted the situation to a correspondent of Le Monde, "whose report was then carried on Radio Free Europe". Both Michnik and Szlajfer were expelled from the university. Upon their expulsion, students organized demonstrations, which were brutally suppressed by the riot police and "worker-squads".