Esegels (aka Izgil (), Äsägel, Askel, Askil, Ishkil, pinyin Asijie, Sijie) were a, possibly,Turkic dynastic tribe that in the Middle Ages joined the Itil Bulgaria state and were assimilated to Bulgars; or was possibly a Bulgar tribe all along, as mentioned by Ibn Fadlan. Numerous records about Esegels in the sources in many languages, in connection with many historical subjects, and across the span of the Eurasian steppes left numerous variations of their name. M.Räsänen suggested Uralo-Altai etymology of this word: Es-kil, Es-gil "Old city", which may conflict with the older Chinese phonetization pinyin: Asijie.
Esegels were mentioned in the Chronography of Theophanes the Confessor (760-818): "the same month (July 563) ambassadors of Askil/Askel, the king of Hermihions (Greek Ερμηχιονιονων; Lat. Ermechionorum), a tribe living among barbarians near the ocean, came to Constantinople".
A Chinese annalistic account in 651 CE of the Western Turkic Khaganate Western Wing (on-shadapyt, Ch. Nushibi 弩失畢) division onto 5 tribes listed Esegels with a notation that the leader of first tribe Qiue-syjin "was most prosperous and strong, the number of his soldiers reached several tens of thousands". The leaders of the 5 tribes were listed as follows:
Esegels may have had connection with the Central Asian tribe Chigil or Ishkil.
Esegel presence in Itil (Volga) Bulgaria in 9th and 10th centuries was also mentioned by Ibn Fadlan. Report of the ambassador Ahmed ibn Fadlan, who visited Itil (Volga) banks in the 921-922, mentioned the Bulgarian tribe Askel.
Among other writers who mentioned Esegels, the Persian “Geography“ of 982 named Ishkils as one of three Bulgarian tribes, who were constantly conflicting among themselves. Gardizi, the author of the composition Zain al-ahbar (mid-11th century), wrote: "Between possessions of Bulgars and possessions of Eskels, who also belong to Bulgars, is a Magyar area. These Magyars are also a Türkic tribe". Constantine Porphyrogenitus wrote that endoethnonym of the "Magyar Türks" was Savartoiaskaloi, i.e. Savart (Suvar/Sabir) and Eskel. Yu.A.Zuev summarized that It is held that Eskels (Esegels) merged with Hungarians (Magyars). The ethnographic group Sekei (written form Szekler) are recognized as their descendants. Esegels left a prominent trace in the Northern and Western Europe as last and first names, mostly in the form "Askel".