Omurtag (or Omortag) (Bulgarian: Омуртаг; original Greek: Μορτάγων and Ομουρτάγ) 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 Eastern Roman 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 the Bulgarian architecture with a number of significant construction projects.
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, Ditseng and Tsog 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.
Omurtag (Bulgarian: Омуртаг) is a town at the eastern foot of Stara Planina in northeastern Bulgaria, part of Targovishte Province, situated at 525 m above sea level. It is the administrative centre of the homonymous Omurtag Municipality. As of February 2011, the town has a population of 7,369 inhabitants.
A notable native is Aleksandar Aleksandrov, one of the two Bulgarian cosmonauts.
The area around the modern town has been inhabited since the Neolithic. Part of Justinian I's defensive system in the 6th century, the region gained importance as part of the First Bulgarian Empire due to the proximity to the capitals Pliska and Preslav and the passes of Stara Planina.
The first written evidence of the modern town date from the 17th century, when it was mentioned as the kaza centre Osman Pazarı in Ottoman tax registers. The settlement was a centre of craftsmanship and trade. Osman Pazarı was liberated from Ottoman rule on 27 January 1878 by Russian troops under Johann Casimir Ehrnrooth during the Russo-Turkish War of 1877-78. Most of the Turkish inhabitants of the town left to be replaced by Bulgarians from around Tran and Kyustendil. Omurtag acquired its present name in 1934, named after Bulgarian khan Omurtag.