Marcian, Marcianus, or Markianos (Μαρκιανός) was a Byzantine and Eastern Roman emperor of the 5th century. He was known for revoking treaties with the Huns under Attila and defeating them in battle. He also famously oversaw the Council of Chalcedon which condemned Monophysitism and canonized Dyophisitism as the Orthodox Christological understanding of Christ's natures.