Johann Rudolf Rocker (German: [ˈʁɔkɐ]; March 25, 1873 – September 19, 1958) was a German anarchist writer and activist. He was born in Mainz to an artisan family.
His father died when he was a child, and his mother when he was in his teens, so he spent some time in an orphanage. As a youth he worked as a cabin boy on river boats and was then apprenticed as a typographer. He became involved in trade unionism and joined the Social Democratic Party of Germany (SPD) before coming under the influence of anarchists such as Mikhail Bakunin and Peter Kropotkin. With other libertarian socialist youth, he was expelled from the SPD, and his anarchist activism led to him fleeing Germany for Paris, where he came into contact with syndicalist and anarchist ideas and practices. In 1895, he moved to London. Apart from brief spells in Liverpool and elsewhere, he remained in East London for most of the next two decades, acting a key figure in the Yiddish-language anarchist scene there, including editing the Arbeter Fraynd periodical, publishing the key thinkers of anarchism, and organising strikes in the garment industry. In London, he formed a life partnership with Milly Witkop, a Ukraine-born anarchist from a Jewish background. During World War I, he was interned as an enemy alien and at the end the war he was deported to the Netherlands.