Marathesium or Marathesion (Ancient Greek: Μαραθήσιον) was a town of ancient Ionia on the coast south of Ephesus, and not far from the frontiers of Caria, whence Stephanus of Byzantium calls it a town of Caria. It is also mentioned in the Periplus of Pseudo-Scylax and by Pliny the Elder. The town belonged to the Samians; but at some time they made an exchange, and, giving it to the Ephesians, receiving in return the Neapolis. It was a member of the Delian League since it appears in tribute records of Athens between the years 443/2 and 415/4 BCE.
- Stephanus of Byzantium, Ethnica, §M431.16
- Stephanus of Byzantium. Ethnica. Vol. s.v.
- Pliny. Naturalis Historia. Vol. 5.31.
- Strabo. Geographica. Vol. xiv. p.639. Page numbers refer to those of Isaac Casaubon's edition.
- Mogens Herman Hansen & Thomas Heine Nielsen (2004). "Ionia". An inventory of archaic and classical poleis. New York: Oxford University Press. p. 1082. ISBN 0-19-814099-1.
- Athenian Tribute Lists, §269
- Athenian Tribute Lists, §290
- Richard Talbert, ed. (2000). Barrington Atlas of the Greek and Roman World. Princeton University Press. p. 61, and directory notes accompanying.
- Lund University. Digital Atlas of the Roman Empire.