The sovereign prince of Monaco (; ) is the monarch and head of state of the Principality of Monaco. All reigning princes and princesses have taken the name of the House of Grimaldi. When Prince Rainier III died in 2005, he was Europe's longest reigning monarch. The Grimaldi family, which has ruled Monaco for eight centuries, is Europe's longest-ruling royal family.
Powers of the prince
Monaco, along with Liechtenstein and Vatican City, is one of only three states in Western Europe where the monarch still plays an active role in day-to-day politics.
The Prince of Monaco exercises his authority in accordance with the Constitution and laws. He represents the principality in foreign relations, and any revision, either total or partial, of the Constitution must be jointly agreed to by the monarch and the National Council.
Legislative power is divided between the Prince who initiates the laws, and the National Council which votes on them. Executive power is retained by the monarch, who has veto power over all legislation proposed by the National Council.
Titles and styles
The Prince is styled His Serene Highness. Although used only formally, the Prince also bears several other hereditary titles, some of which are occasionally bestowed on his relatives or their spouses. Some of these titles have merged with the Crown of Monaco as a result of the Grimaldi family's acquisition of various fiefs;
The tradition of the monarchy of Monaco was that the flag flying from the staff on the tower above his office be hoisted when the prince was present in Monaco.