Established by Clara Zetkin, Käte Duncker, and others, International Women's Day was first observed.

Clara Zetkin was a German Marxist theorist, communist activist, and advocate for women's rights.

Käte Duncker was a German political and feminist activist who became a politician in the Social Democratic Party of Germany and then the Communist Party of Germany.

International Women's Day (IWD) is celebrated on 8 March, commemorating women's fight for equality and liberation along with the women's rights movement. International Women's Day gives focus to issues such as gender equality, reproductive rights, and violence and abuse against women. Spurred by the universal female suffrage movement, International Women's Day originated from labor movements in Europe and North America during the early 20th century.