Mnaseas of Patara was a Greek geographer and historian of the 3rd century BCE. He originated from Patara in Lycia and was a student of Eratosthenes of Cyrene in Alexandria. No further biographical details survive.

His works are lost and known only through fragments. He authored a geographical treatise, the Periplous or Periegesis, which described a circuit of Europe, Asia, and Libya, as well as a more focused Periplus of Europe. Later authors, such as the paradoxographer Antoninus Liberalis, cite him for regional myths and wondrous tales, indicating his writing blended geography with ethnography and local lore.

Mnaseas represents the Hellenistic geographical tradition where factual description intersected with collected mythology. His significance lies in his later use as a source, preserving fragments of cultural and geographical knowledge through compilers like Antoninus. His tutelage under Eratosthenes also places him within the influential Alexandrian scholarly network.