| Ivan Asen I Иван Асен I | |
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 Coin of Ivan Asen I | |
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| Reign | 1187/1188 – 1196 |
| Predecessor | Peter II |
| Successor | Kaloyan |
| Died | 1196 Tarnovo |
| Spouse | Elena |
| Issue |
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| Dynasty | Asen dynasty |
Ivan Asen I, also known as Asen I or John Asen I (Bulgarian: Иван Асен I; died in 1196), was emperor or tsar of Bulgaria from 1187/1188 to 1196 as co-ruler with his elder brother, Peter II. Hailing from the Byzantine theme of Paristrion, his exact place and date of birth are unknown. Most contemporaneous chronicles describe Asen and his brothers, Theodor (Peter) and Kaloyan, as Vlachs but they were probably of mixed Bulgarian, Cuman and Vlach ancestry.
In 1185, Asen and Theodor went to see the Byzantine Emperor Isaac II Angelos in Thrace to demand an estate in the Balkan Mountains. After the Emperor refused and humiliated them, the brothers persuaded their Bulgarian and Vlach compatriots to rise up against the Byzantine Empire. Before the end of the year, Theodor was crowned Emperor of Bulgaria, taking the name Peter. After Isaac II defeated them in early 1186, Asen and Peter fled north over the Danube but returned in the autumn, accompanied by Cuman reinforcements. They captured Paristrion and began pillaging the nearby Byzantine territories.
Asen became his brother's co-ruler in 1187 or 1188. They divided their realm around 1192, with Asen receiving Tarnovo and its region. Asen made a series of raids against Byzantine territories and expanded his rule over the lands along the Struma River in the early 1190s. A boyar, Ivanko, stabbed him to death in 1196.