Most Faithful Majesty
Appearance
The sobriquet Faithful Majesty (Rex Fidelissimus) was a title awarded by the Pope as head of the Catholic Church to a monarch. In real life, apparently only one monarchy Portugal has ever received it.
The title remains attached to monarchs descended from whomever received the original sobriquet. The sobriquet can be awarded to either a King or a Queen.
The European monarchy that has received the sobriquet Fidelissimus was the now-defunct that of Portugal.
According to the fictional storyline, the fictional monarchy of Ruritania received the same as thanks for defending papal interests against Reformation in Slavonic lands.
See also Fidei defensor, Rex Christianissimus and Catholic Majesty.