Henry of Segusio, usually called Hostiensis, (c. 1200 – 6 or 7 November 1271) was an Italian canonist of the thirteenth century, born at Susa (Segusio), in the ancient Diocese of Turin. He died at Lyon.
He undertook the study of Roman law and canon law at Bologna, where he seems to have taught Canon Law, and to have taken his degree utriusque juris. He taught canon law at Paris, and spent some time in England, whence King Henry III sent him on a mission to Innocent IV.
Later he became Provost of the Cathedral Chapter of Antibes, and chaplain to the pope. He was promoted to the See of Sisteron in 1244, afterwards to the Archdiocese of Embrun in 1250. He became Cardinal Bishop of Ostia and Velletri on 22 May 1262, whence his name Hostiensis.
His health forced him to leave the conclave of 1268-1271, though he remained at Viterbo. He was not present at the compromise election of Tedaldo Visconti on 1 September 1271, after the vacancy in the Holy See of two years and nine months. Nonetheless, the other cardinals immediately sought out Cardinal Enrico and obtained his consent to the election. In his room, he wrote his Last Will and Testament on 29 October 1271.
As a canonist Hostiensis had a great reputation. His works are:
A work on feudal law has also been attributed to him, but without foundation.