Tervel (Bulgarian: Тервел) also called Tarvel, Terval, or Terbelis in some Byzantine sources, was the khan of the Bulgars during the First Bulgarian Empire at the beginning of the 8th century. In 705 Emperor Justinian II named him caesar, the first foreigner to receive this title. He was raised a pagan like his grandfather Khan Kubrat, but was later possibly baptized by the Byzantine clergy. Tervel played an important role in defeating the Arabs during the Siege of Constantinople in 717–718.
The Nominalia of the Bulgarian khans states that Tervel belonged to the Dulo clan and reigned for 21 years. According to the chronology developed by Moskov, Tervel would have reigned 695–715. Other chronologies place his reign in 701–718 or 700–721, but cannot be reconciled with the testimony of the Imennik. The testimony of the source and some later traditions allow identifying Tervel as the son and heir of his predecessor Asparukh, who had perhaps died in battle against the Khazars.