Časlav of Serbia

Tzeésthlabos (Greek: Τζεέσθλαβος), usually transliterated as Časlav (Serbian Cyrillic: Часлав) or Chaslav and Tzeeslav,^[a] was Prince of the Serbs from c. 933 until his death in c. 943/960.^[b]

Časlav was the son of Klonimir, a son of Strojimir who ruled as co-prince in 851–880. He belongs to the first Serbian dynasty, the Vlastimirovićs (ruling since the early 7th century), and is the last known ruler of the family. His mother was a Bulgarian noblewoman chosen as wife of Klonimir by Boris I of Bulgaria himself.

Initially an ally of the Bulgarians, Časlav successfully came to the throne of Serbia in a very chaotic period of history, managing to reorganize and repopulate the country after Bulgarian–Serbian wars of 917–924. He was a vassal of the Byzantine Empire. A possible identification with a same-named person from the Chronicle of the Priest of Duklja reveals that he presumably fought off the Magyars, but eventually dying in combat with them. Časlav is remembered, alongside his predecessor Vlastimir, as founders of Serbia in the Middle Ages.