Marcian of Heraclea was a Greek geographer of the 4th or 5th century CE from Heraclea Pontica on the Black Sea. A compiler and epitomizer rather than an original explorer, he had access to a significant library of earlier geographical texts. He is often associated with revising the work of Ptolemy and is distinguished by epithets like "the Younger" from an earlier, possibly homonymous, author.

His three known works are epitomes of earlier geographies. These include an Epitome of Menippus of Pergamon's Periplus of the Inner Sea, an Epitome of Artemidorus of Ephesus's Geography, and a two-book Periplus of the Outer Sea describing Atlantic and Indian Ocean coasts based on Ptolemy. All survive only in fragments preserved in Byzantine manuscripts and the Suda lexicon.

Marcian’s significance lies in his role as a transmitter of knowledge. His compilations preserve summaries of now-lost Hellenistic and Roman geographical works, providing modern scholars with indirect evidence of earlier science and exemplifying the late antique scholarly tradition of epitomizing authoritative texts.