The siege of Adrianople (Bulgarian: Обсада на Одрин) in 813 was a part of the wars of the Byzantine Empire with the BulgariankhanKrum (Byzantine-Bulgarian Wars). It began soon after the Byzantine field army was defeated in the battle of Versinikia on June 22. At first the besieging force was commanded by Krum's brother (whose name is not mentioned in the primary sources). The khan himself went on with an army to Constantinople. After an unsuccessful Byzantine attempt to murder him ruined all prospects for negotiations with them, Krum ravaged much of Eastern Thrace and then turned against Adrianople which was still under siege. The city—one of the most important Byzantine fortresses in Thrace—held out for a while despite being attacked with siege engines. Yet, without any help from outside, the garrison was forced to capitulate due to starvation. On Krum's order the population of Adrianople and the surrounding area (numbering about 10,000) was transferred to Bulgarian territory north of the Danube.
Under the peace treaty, concluded in 815, Adrianople remained in the Byzantine empire.