Robert Dißmann (8 August 1878 – 30 October 1926) was a German trade unionist and politician.
Born in Hülsenbusch, Dißmann became a machinist and joined the German Metal Workers' Union (DMV) and the Social Democratic Party of Germany (SPD).
In 1900, he began working on a full-time basis for the union in Barmen.
In 1917, he left the SPD and joined the new Independent Social Democratic Party of Germany (USPD).
He rejoined the SPD with the majority of the USPD in 1922, and remained prominent in its left-wing faction.