Regnal name

name chosen by a reigning monarch, different from their original secular name

A regnal name, or reign name, is a formal name or label which refers to the years of the reign of a monarch or a pope.

A monarch sometimes chooses a reign name which is different from his or her personal name.

Example: Edward VII of the United Kingdom, born Albert Edward of Saxe-Coburg and Gotha

A pope chooses a regnal name when he is elected. It becomes his new personal name.

Example: Pope John Paul II, born Karol Józef Wojtyła,

The new name -- or sometimes the old one -- is followed by an ordinal number to create a unique name for the period in which the monarch is on the throne.

Example: Elizabeth II was queen of the United Kingdom and many other Commonwealth Realms until her death in 2022
Elizabeth I of England (1533–1603) was the 1st British queen named Elizabeth. She ruled over "Elizabethan" England. Her time on the throne was called the "Elizabethan era" or the "Elizabethan age".