Belgian scholar who was the foremost exponent of biographical church history based on archaeological and documentary work.

He became a Jesuit in 1879 and was ordained priest in 1890, later identifying himself with the work of the Bollandists (q.v.) and becoming their head in 1912.

Delehaye took a decisive part in the census of extant lives of saints, specializing in the early Christian centuries. He edited the Bibliotheca Hagiographica Graeca (1895; “Library of Greek Hagiographies”), but his fame rests on those books directed to historians in general on the critical method as applied to the lives of saints, of which the best known are: Les Légendes hagiographiques (1905; The Hagiographical Legends, 1962); Les Origines du culte des martyrs (1912); Les Passions des martyrs et les genres littéraires (1921); and Sanctus (1927). He edited the Constantinople Synaxarium (1902), explained verbatim the Martyrologium Hieronymianum (1931; “The Martyrology of Jerome”), and took the leading part in the Bollandists' commentary on the Martyrologium Romanum (1940). He was a constant contributor to Acta Sanctorum (“Acts of the Saints”), Analecta Bollandiana, (“The Bollandists' Collection”), and other learned journals.