Gregory XIII.

Gregory XIII., born in Bologna; was skilled in canon law; distinguished himself in the Council of Trent, and by his zeal against the Protestants; celebrated the Bartholomew Massacre by public thanksgivings in Rome, and reformed the calendar.

Definition taken from The Nuttall Encyclopædia, edited by the Reverend James Wood (1907)

Gregory IX., Ugolino * Gregory XVI.
[wait for the fun]
Greg, William Rathbone
Grégoire, Henri
Gregorian Calendar
Gregorian Year
Gregory I., the Great
Gregory II., St.
Gregory III.
Gregory VII., Hildebrand
Gregory IX., Ugolino
Gregory XIII.
Gregory XVI.
Gregory Nazianzen, St.
Gregory of Nyssa, St.
Gregory of Tours, St.
Gregory Thaumaturgus, St.
Gregory, David
Gregory, James
Gregory, James
Gregory, John
Gregory, William