Yuhanna ibn Masawaih, , also written Ibn Masawaih, Masawaiyh, and in Latin Janus Damascenus, or Mesue, Masuya, Mesue Major, Msuya, and Mesuë the Elder was a Persian or Assyrian East Syriac Christian physician from the Academy of Gundishapur. According to The Canon of Medicine for Avicenna and 'Uyun al-Anba for the medieval Arabic historian Ibn Abi Usaybi'a, Masawaiyh's father was Assyrian and his mother was Slavic.

Assyrians are an indigenous ethnic group native to Mesopotamia, a geographical region in West Asia. Modern Assyrians descend directly from Ancient Mesopotamians such as ancient Assyrians and Babylonians. Modern Assyrians may culturally self-identify as Syriacs, Chaldeans, or Arameans for religious, geographic, and tribal identification.