Znak was an association of lay Catholics in Poland, active between 1956 and 1976. It was the only Catholic organisation supported both by the PZPR Communist party and the Catholic hierarchy.

It was created as one of several smaller groups that sprung up after dissolution of the communist-controlled association PAX of Bolesław Piasecki in 1956. It was granted with several seats in the Polish Sejm and was intended as a link between the Catholic Church and the state. As such it was allowed to cooperate with various Western European catholic movements, among them the German section of the International Catholic Peace Movement Pax Christi .

It was composed of the members of Klub Inteligencji Katolickiej (Club of Catholic Inteligentsia) and journalists of Tygodnik Powszechny newspaper. Among the most prominent members of Znak were:

• Tadeusz Mazowiecki
• Jerzy Zawieyski
• Stefan Kisielewski
• Stanisław Stomma
• Wanda Pieniężna
• Jerzy Zawieyski

During the March 1968 anti-Semitic and anti-inteligentsia campaign of Władysław Gomułka, Znak was the only political organisation in Sejm to protest against it. In 1976 member of Znak, Stanisław Stomma , was one of the only two Members of Parliament not to approve the ammendment of Polish constitution underlining the role of the communist party and the alliance with USSR. As a reprisal the Znak was disbanded.

A remainder of the group existed until 1980 when it was renamed to Polski Związek Katolicko-Społeczny.