Louis II was Prince of Monaco from 26 June 1922 to 9 May 1949.

The sovereign prince 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.