Omurtag (or Omortag) (died 831) also known as Murtag or Murtagon (; ) was a Great Khan (Kanasubigi) of Bulgaria from 814 to 831. He is known as "the Builder".
In the very beginning of his reign he signed a 30-year peace treaty with the neighboring Byzantine Empire which remained in force to the end of his life. Omurtag successfully coped with the aggressive policy of the Frankish Empire to take Bulgaria's north-western lands and suppressed the unrest among several Slavic tribes. He made administrative reforms which increased the power and the authority of the central government. His reign was marked with a strong development of Bulgarian architecture with a number of significant construction projects.
Rise to the throne
After the death of Khan Krum there was a short period of political instability in the country. Some sources mention that Bulgaria was ruled by three nobles - Dukum (Δούκουμος; may be identical with Omurtag), Ditzeng ( Δίτζενγος; from Bulgar Di-jevğu/jabğu? according to Peter B. Golden), it could also rather be a title of Tsokos, according to H. Grégoire, compare ičirgü-boulias; and Tsog (Τζóκος?; compare Bulgar Coğ, ǰoɣ 'funeral feast'). It's been theorized that any of these names may also be synonyms with one another - who were recorded as persecutors of the Christians in the Byzantine sources. Several theories exist about the events in that period. According to them, those three nobles were either Krum's generals with a major role in the government but without assuming the throne; or regents to the infant Omurtag. The historians usually accept as a compromise the view of Professor Vasil Gyuzelev that Omurtag succeeded his father after short disturbances in the government.
Foreign policy
First years of Omurtag
thumb|right|The Bulgarian ruler Omurtag sends delegation to the Byzantine emperor.
thumb|right|Omurtag pursues Thomas the Slav.
After the abrupt death of Khan Krum there were many Bulgarian troops in Thrace defending different strategic locations. The Byzantine Emperor Leo V the Armenian made use of the short crisis in the summer of 814 and led his troops against the Bulgarians. In the ensuing battle near the town of Burtodizos (probably the modern Babaeski) the Byzantines were victorious - Omurtag escaped the battlefield on his swift horse. However, the battle was not a decisive blow for the Bulgarians although it certainly had some effect .
thumb|right|Greek Inscription bearing the words "kanas bigiom ourtag" (Kanas(u)bigi Omurtag) in the first two lines. [[Pliska, Bulgaria.