The Head of the Royal House of Karageorgevitch is the Hereditary Protector of the OSJ. The last Royal Protector of the Order was His Late Majesty King Peter II of Yugoslavia.

Petar Karadordevic was a direct descendant of Czar Paul I and a nephew of Queen Marie Alexandra Victoria of Romania, who was the granddaughter of Czar Alexander II whose grandfather was Czar Paul I, 70th Grand Master of the Order of St John of Jerusalem, Knights Hospitaller.

Born in Belgrade on September 6th, 1923, he was the son of King Alexander I of Yugoslavia and Princess Maria of Romania.

In 1962, the former Prior of France and Lieutenant Grand Master Colonel Paul de Granier Cassagnac asked King Peter for confirmation of the Royal Hereditary Protectorate for the Order of  St. John of Jerusalem. The official ceremony took place in Grandson castle, on Lake Neuchatel, in Switzerland on April 6th of that year.  However, nine months earlier, on July 24th, 1961, in a solemn ceremony in Monaco, the King had already indissolubly tied himself to the Order.

When King Peter agreed to take the Order under his royal protection in January 1962 he must have had in mind the need for a constituion suitable for an Order of Chivalry.  As it was constituted at the time, the OSJ did not have such an instrument, but relied on the 1912 document drawn up by the hereditary knights and other members who had settled in the U.S.

His greatest achievement as Royal Protector was his grant of a new Royal Charter in 1963 and the Constitution of 1964.

He was elected the Order’s 73rd Grand Master in 1965 and died in 1970. The position of Royal Protector has not been offered to another since his death.