Wilhelm Hasenclever (19 April 1837 in Arnsberg, Westphalia Province – 3 July 1889 in Berlin-Schöneberg) is a German politician.

Originally a tanner by trade, he later becomes a journalist and author.

However, he is most well known for his political work in the predecessors of the Social Democratic Party of Germany (SPD).

In 1869 and 1870, Hasenclever is a representative for the General German Workers' Association (Allgemeiner Deutscher Arbeiterverein, ADAV) in the Reichstag (parliament) of the North German Confederation.

From 1871 on, he is the last president of the ADAV, until it merges with the Social Democratic Workers' Party (Sozialdemokratische Arbeiterpartei, SDAP) to form the Socialist Workers' Party of Germany (Sozialistische Arbeiterpartei Deutschlands, SAP).

From 1874 to 1888 he is again a social democrat representative in the Reichstag of the German Empire that had been formed in 1871: Originally for the ADAV, later for the SAP.

Hasenclever is a member of the party board there as well.

Together with Wilhelm Liebknecht, he also founds the party paper Vorwärts, the official newspaper of the SPD until the 1990s.