Rhamnous (Ancient Greek: Ῥαμνοῦς, romanized: Rhamnoûs; Modern Greek: Ραμνούς, romanized: Ramnoús), also Ramnous or Rhamnus, was an ancient Greek city in Attica situated on the coast, overlooking the Euboean Strait. Its ruins lie northwest of the modern town of Agia Marina in the municipality of Marathon.
The site was best known in antiquity for its sanctuary of Nemesis, the implacable avenging goddess, her most important in ancient Greece.