The Asen dynasty and the Second Bulgarian Empire rose as the leaders of a rebellion against the Byzantine Empire at the turn of the year 1185/1186 caused by the increase in the Imperial taxes.
Early rulers from the Asen dynasty (particularly Kaloyan) referred to themselves as "Emperors of Bulgarians and Vlachs". Later rulers, especially the successful Ivan Asen II, styled themselves "Tsars (Emperors) of Bulgarians and Greeks".
Some members of the Asen family entered Byzantine service in the thirteenth to fourteenth centuries. The name also occurs as a family name in modern Greek, and could go back to the same name.
The Sratsimir dynasty descends paternally from the Asen dynasty.
The origins of the dynasty, especially the ethnic background of the three Asen brothers (Teodor I Peter IV, Ivan Asen I and Kaloyan) are still a source of much controversy, debated between historians. There are three main hypothesis regarding their origins:
- Bulgarian origin, a view that is common among the Bulgarian historians who reckon that all native sources use predominantly the terms Bulgaria, Bulgarians and Bulgarian, that tsar Kaloyan claimed provenance from the rulers of the First Bulgarian Empire.
- Vlach origin, a view supported by historians who base their claims on mentions in some chronicles.
- Cuman origin,  as some of the names in the dynasty, including Asen and Belgun (nickname of Ivan Asen I) are derived from Cuman language.
In their own administrative documents and correspondence, the three rulers viewed themselves as descendants and successors of the Bulgarian Tsars Samuil, Peter I and Simeon I, and the state they founded as a continuation of the First Bulgarian Empire. However, this could be just a way to proclaim their legitimacy for the throne of the Empire.
In a correspondence, of 1199, the Pope talks about the "Roman descent" of Kaloyan. However, considering the actual text says "Nos autem audito quod de nobili urbis Romae prosapia progenitores tui originem traxerint" ("We heard that your forefathers come from a noble family from the city of Rome"), it's usually dismissed as simply a hidden compliment of the Pope to Kaloyan.
Pope Innocent III in his letter to the Bulgarian King Kaloyan (Calojoannes) in 1204 addressed him “King of Bulgarians and Vlachs (Bulgarorum and Blacorum rex) ; in answering the Pope, John calls himself “imperator omnium Bulgarorum et Blachorum” but signs himself “imperator Bulgariae Calojoannes” the archbishop of Trnovo calls himself “totius Bulgariae et Blaciae Primas"
The name of the dynasty comes from one of the brothers, namely Asen I. The etymology is most likely of Cuman Turkic origin, derived from "esen" which meant "safe, sound, healthy" and the Belgun nickname seems to be derived from Turkic "bilgün", which meant "wise". Further support to this connection can be found in the charters of the Great Lavra of Mt. Athos from the end of the 12th century, which mention the monastery's problems with some of the Cuman stratiotes, where "Asen" is listed as the name of one of those Cumans. 
Rulers from the Asen dynasty
|Ivan Asen I (Asen)||1187 - 1196|
|Peter IV (Teodor)||1186 - 1197|
|Kaloyan (Ioanitsa)||1197 - 1207|
|Boril (Boril Kaliman)||1207 - 1218|
|Ivan Asen II||1218 - 1241|
|Kaliman I Asen (Koloman)||1241 - 1246|
|Michael II Asen||1246 - 1256|
|Kaliman II Asen (Koloman)||1256|
|Mitso Asen||1256 - 1257|
|Constantine Asen (Konstantin Tih)||1257 - 1277|
|Ivan Asen III||1279 - 1280|
- Humanitas 2008: 4
- István Vásáry (2005) Cumans and Tatars, Cambridge University Press, p. 2
- Laurențiu Rădvan, At Europe's Borders: Medieval Towns in the Romanian Principalities, BRILL, 2010, p. 129
- The Cambridge History of Early Inner Asia, Volume 1, Denis Sinor, pg 279.
- Ion Grumeza, The Roots of Balkanization: Eastern Europe C.E. 500-1500 (2010), p.51.
- Bulgarian Folk Customs, Mercia MacDermott, pg 27
- Plamen Pavlov - "Scythian chieftains in the fields of Bulgaria, 11th-12th century (in Bulgarian)
|Wikimedia Commons has media related to Asen dynasty.|
- Božilov, Ivan (1985). Familijata na Asenevci (1186–1460) (in Bulgarian). Sofia: Bulgarian Academy of Sciences. OCLC 14378091.
- Vasary, Istvan (2005) "Cumans and Tatars", Cambridge University Press: pp. 34–42
- Stephenson, Paul (2000) "Byzantium's Balkan Frontier — A Political Study of the Northern Balkans, 900–1204" pp. 289–300
- History of the Byzantine Empire, A. A. Vasiliev 1935
- Djuvara, Neagu (2008). O scurta istorie a romanilor povestita celor tineri. Humanitas. ISBN 978-973-50-2591-5.
- Stelian Brezeanu, Istoria Imperiului Bizantin, Bucuresti, MERONIA, 2007