Sixtus ( or Sike; died 1285 or 1286) was a Hungarian clergyman in the 13th century, who served as a skilled diplomat of King Béla IV of Hungary for decades. Early life Sixtus was presumably born around 1220 into a lower noble family, which possessed lands and fields in Hetény (today Chotín in Slovakia). His permanent honorary title of "magister" demonstrates his university degree (possibly he studied in Sorbonne or other Paris-type cathedral schools, gaining rhetorical and legal erudition). In contemporary records, he is first referred to as a cleric by Pope Innocent IV on 20 February 1245, when he authorized papal legate Giacomo da Pecorara to permit Sixtus' consecration and to grant him the right of possession of church benefices despite his "lack of origin". The document says Sixtus was the son of a lowborn priest. Sixtus had a sister Joanna, who married Lawrence, a landowner in Szőllős (today Vinodol, Nitra). Their marriage produced several children. His other brother-in-law Ampud of Macsala was also a landowner in Hetény. Through the paternal branch, he was related to Mikó Szécs, a courtier in Esztergom. Ecclesiastical career Historian Péter Kis assumes Sixtus was identical with a namesake cleric who is mentioned as a cantor of the Győr Chapter by four charters in the period between 1241 and 1248. He also argues Sixtus functioned as dean of Pressburg Chapter in 1253. Sixtus is first referred to as lector of the Esztergom Chapter in 1255. Through his extensive kinship in Esztergom County, he could compensate his nuclear family's relatively low origin. Besides his duty to proclaim the Scripture readings used in the Liturgy of the Word, Sixtus was responsible for management of the cathedral school of Esztergom and teaching the clerics and the poor scholars, in accordance with Canon 18 of the Third Council of the Lateran (1179). Thus he was also styled as "scholasticus" in contemporary documents. Additionally, Sixtus led the local place of authentication in this capacity. Approximately thirty charters remain from Sixtus' term. For this role, Charles I of Sicily referred to him as "chancellor of Esztergom" () in 1270. Sixtus occasionally also used this title thereafter. Sixtus resigned as lector, when he was sent as head of the Hungarian diplomatic mission to Rome, from 1258 to 1264. Then he became archdeacon of Komárom (present-day Komárno, Slovakia). On 15 July 1264, Pope Urban IV ordered Vincent, Bishop of Nyitra (or Nitra)