Marx is a Germanised rendering of the Jewish family name Mordechai. It is derived from the Latin Marcus. Notable people with this surname include:
- Jenny Marx (née Jenny von Westphalen), wife of Karl Marx
- Karl Marx, 19th Century Communist philosopher
- Eleanor Marx, youngest daughter of Karl and Jenny Marx
- Heinrich Marx, father of Karl Marx
- Henriette Marx (née Presburg or Pressburg), mother of Karl Marx
- Jenny Longuet (née Jenny Marx), eldest child of Karl and Jenny Marx
- Laura Lafargue (née Laura Marx), second daughter of Karl and Jenny Marx
- The Marx Brothers, a Statesian family comedy act
- Wilhelm Marx, a Centre Party politician who served as Chancellor of Germany twice