A hagiography is a biography of a saint or leader, or an adulatory and idealized biography of a founder, saint, monk, nun or icon in any of the world's religions. Early Christian hagiographies might consist of a biography or vita, a description of the saint's deeds or miracles or martyrdom or a combination of these.
By extension the word has come to mean an excessively flattering biography of a person that the author wishes to promote.