thumb|De consolatione medicinarum, 1475
Yuhanna ibn Masawaih (circa 777–857), (), also written Ibn Masawaih, Masawaiyh, and in Latin Janus Damascenus, or Mesue, Masuya, Mesue Major, Msuya, and Mesuë the Elder was a Persian physician, trained by Jabril ibn Bukhtishu, who was a member of the Church of the East, from the Academy of Gondishapur. According to The Canon of Medicine for Avicenna and <nowiki>'</nowiki>Uyun al-Anba for the medieval Arab historian ibn Abi Usaybi'a, Masawaiyh's father was from Khuzestan and his mother was a Slav.
Life
thumb|left|Mesue
Born in 777 as the son of a pharmacist and physician from Gundeshapur, he came to Baghdad and studied under Jabril ibn Bukhtishu. He translated various Greek medical works into Syriac, but wrote his own work in Arabic.