Kir Stefan the Serb (second half of the 14th and 15th century) was a Serbian monk, protopsaltos, musicologist, choirmaster and more importantly, composer of the chants developed within the sphere of the activities of Byzantine culture in the Serbian state. Together with (but independently from) Isaiah the Serb and Nikola the Serb he followed faithfully the Byzantine musical traditions, writing in the late kalophonic style of the 14th and 15th centuries. With his distinctive compositional style, he is one of the earliest (if not the earliest) identifiable Medieval Serbian composers and also one of the original founders of new and distinctive style called Serbo-Byzantine school.