Hippolyte Delehaye (1859–1941), a Belgian Jesuit and foremost expert in hagiography, devoted his life to the study of the lives of Christian saints and the advancement of critical approaches to the field. As a leading figure in the Society of Bollandists, he oversaw the editing of important works such as the Bibliotheca Hagiographica Graeca and made significant contributions to the Acta Sanctorum, enhancing the academic scrutiny of martyrological texts.
His major works, including Les Légendes hagiographiques (1905) and Sanctus (1927), examine the beginnings and literary structures of saintly veneration, illustrating his dedication to thorough historical inquiry. During the Church's 20th-century discussions on critical scholarship, Delehaye's research continues to serve as a foundational reference for understanding the development of hagiographic traditions and their theological significance.