Edgar Gerhard Julius Oscar Ludwig von Westphalen (26 March 1819 – 30 September 1890) was a German writer and Communist politician, who was also a long-time friend and brother-in-law of Karl Marx.

He was the son of Prussian baron Ludwig von Westphalen and his second wife Caroline Heubel.

Heubel was also the mother of Jenny who married Karl Marx.

[1] The Westphalen and Marx families were neighbors in Trier, with Karl and Edgar being friends and schoolmates.

[3] Westphalen was an early member of the Communist Correspondence Committee's Brussels' circle and later one of the founding members of the Communist League.