Ernst Herman ridder van Rappard (born 30 October 1899 in Banyumas Regency, Central Java, Dutch East Indies – died 11 January 1953 in Vught) was a Dutch National Socialist and anti-Semite. After leading his own failed Nazi movement van Rappard enlisted in the Schutzstaffel and saw active service in the Second World War.
Part of a leading Dutch family, van Rappard was born in the Dutch East Indies to chief engineer Oscar Emile ridder van Rappard and his wife Dina Thal Larsenhe, as the younger brother of future sportsman Oscar van Rappard His schooling took place in the Netherlands at The Hague and subsequently at the University of Leiden. He then studied economics in Berlin and Munich and there became supportive of Nazism.
He joined the National Socialist Dutch Workers Party (NSNAP) in 1931, although the group split into three and van Rappard soon found himself as the leader of his own version of the party. His group, the NSNAP-Van Rappard advocated the incorporation of the Netherlands into the Third Reich, arguing that the Dutch had a strong ethnic kinship with the Germans. His group also vied with the National Socialist Movement in the Netherlands (NSB) in terms of its virulent anti-Semitism, drawing most of its support from the Dutch-German border. His group was later renamed NSNAP-Hitlerbeweging, though Adolf Hitler ordered the removal of his name from what was a minor movement.