Wilhelm Hasselmann (September 25, 1844 – February 25, 1916) was a German socialist politician, activist and editor of various social democratic newspapers.
Hasselmann attended the polytechnic school in Hanover and continued his studies in Berlin, where he came in to contact with the rising labour movement in Prussia.
Because of the increasing pressure of the anti socialist and union laws implemented by the Prussian Chancellor Otto von Bismarck, the two formerly competing parties, the General German Workers' Association and the Social Democratic Workers' Party of Germany (SPD) decided to unite in a joint congress initiated by Hasselmann and the spokesperson of the SDAP Wilhelm Liebknecht.
Karl Marx later mockingly referred to Hasselmann as the "Berlin Marat" in his work Critique of the Gotha Programme.
[3] Hasselmann, becoming more of an outcast with his radical positions both in the pro-government conservative circles and within the SAP, remained relatively popular among the poorer working class.