Most Faithful Majesty
Appearance
The sobriquet Most Faithful King (Rex Fidelissimus) was a title awarded by the Pope as spiritual head of the Catholic Church to a to Portuguese monarchy.
The title remains attached to monarchs descended from whoever received the original sobriquet. The sobriquet can be awarded to either a king or a queen.
The only European monarchy that has received the sobriquet Fidelissimus was the now-defunct monarchy of Portugal. King John V of Portugal was favoured with the title of Rex Fidelissimus in 1748 by Pope Benedict XIV.