Paul Grottkau (1846–1898) was a German-American socialist political activist and newspaper publisher. Grottkau is best remembered as an editor alongside Haymarket affair victim August Spies of the Chicagoer Arbeiter-Zeitung, one of the leading American radical newspapers of the decade of the 1880s. Later moving to Milwaukee, Grottkau became one of the leading luminaries of the socialist movement in Wisconsin.