| Boril Борил | |
|---|---|
 Golden seal of Boril | |
| Tsar of Bulgaria | |
| Reign | 1207–1218 |
| Predecessor | Kaloyan |
| Successor | Ivan Asen II |
| Spouse | Cuman princess Elisabeth of Courtenay |
| House | Asen dynasty |
Boril (Bulgarian: Борил) was the emperor (tsar) of Bulgaria from 1207 to 1218. He was the son of an unnamed sister of his predecessor, Kaloyan and Kaloyan's brothers, Peter II and Ivan Asen I, who had restored the independent Bulgarian state. After Kaloyan died unexpectedly in October 1207, Boril married his widow, a Cuman princess and seized the throne. His cousin, Ivan Asen, fled from Bulgaria, enabling Boril to strengthen his position. His other kinsmen, Strez and Alexius Slav, refused to acknowledge him as the lawful monarch. Strez took possession of the land between the Struma and Vardar rivers with the support of Stefan Nemanjić of Serbia. Alexius Slav secured his rule in the Rhodope Mountains with the assistance of Henry, the Latin Emperor of Constantinople.
Boril launched unsuccessful military campaigns against the Latin Empire and the Kingdom of Thessalonica during the first years of his reign. He convoked the synod of the Bulgarian Church in early 1211. At the assembly, the bishops condemned the Bogomils for heresy. After an uprising broke out against him in Vidin between 1211 and 1214, he sought the assistance of Andrew II of Hungary, who sent reinforcements to suppress the rebellion. He made peace with the Latin Empire in late 1213 or early 1214. After Henry died in 1216 and Andrew II left Hungary for a crusade, Ivan Asen returned to Bulgaria. He captured and blinded Boril in Tarnovo in 1218.