The sobriquet Most Faithful King (Rex Fidelissimus) was a title awarded by the Pope

Pope

The Pope is the Bishop of Rome, a position that makes him the leader of the worldwide Catholic Church . In the Catholic Church, the Pope is regarded as the successor of Saint Peter, the Apostle...

 as spiritual head of the Catholic Church

Roman Catholic Church

The Catholic Church, also known as the Roman Catholic Church, is the world's largest Christian church, with over a billion members. Led by the Pope, it defines its mission as spreading the gospel of Jesus Christ, administering the sacraments and exercising charity...

 to a monarch. In practice only one monarchy, Portugal

Portugal

Portugal , officially the Portuguese Republic is a country situated in southwestern Europe on the Iberian Peninsula. Portugal is the westernmost country of Europe, and is bordered by the Atlantic Ocean to the West and South and by Spain to the North and East. The Atlantic archipelagos of the...

, has ever received it.

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

Pope Benedict XIV

Pope Benedict XIV , born Prospero Lorenzo Lambertini, was Pope from 17 August 1740 to 3 May 1758.-Life:...

.

See also

• Fidei defensor
  Fidei defensor
  Fidei defensor is a Latin title which translates to Defender of the Faith in English and Défenseur de la Foi in French...
  
  
• Apostolic Majesty
  Apostolic Majesty
  His Apostolic Majesty was a style used by the Kings of Hungary, in the sense of being latter-day apostles of Christianity.-First creation:The origin of this title dates from about A.D...
  
  
• Rex Christianissimus
• Catholic Majesty