Most Faithful Majesty

Most Faithful Majesty (Sua Majestade Fidelíssima) was the title used by the Portuguese monarchs, from 1748 to 1910.

The sobriquet Most Faithful King (Rex Fidelissimus, Rei Fidelíssimo) was a title awarded by the Pope Benedict XIV – as spiritual head of the Catholic Church – in 1748, to the King John V of Portugal and to his heirs.

The title Fidelissimus 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 was the now-defunct monarchy of Portugal.

Similar titles
The monarchs of other countries have received similar titles from the Pope:
 * Hungary: Apostolic Majesty (awarded c. 1000)
 * Venice: Most Serene Republic
 * France: Most Christian Majesty (awarded c. 1380)
 * Spain: Most Catholic Majesty (awarded in 1493)
 * England: Defender of the Faith (awarded in 1521 and revoked again c. 1530 by the Pope. Granted again in 1543 by the Parliament of England.)
 * Poland: Orthodox Majesty (awarded in 1661)
 * Germany: Defensor Ecclesiae (Protector of the Church; awarded to Holy Roman Emperors)