Rainier I of Monaco was the first sovereign Grimaldi ruler of the area now known as Monaco. He also held the title of Lord of Cagnes. Cagnes was the town where in 1309 he established a stronghold, today known as the Château Grimaldi.
Additionally, he was Baron of San Demetrio (Kingdom of Naples). He was the eldest of the three sons of Lanfranco Grimaldi, French Vicar of Provence, by his wife, Aurelia del Carretto (who later remarried her husband's nephew, François Grimaldi).
Rainier joined his stepfather (François) and a group of men to take the castle on the Rock of Monaco; the event is commemorated on the Monegasque coat of arms, where the supporters are two monks armed with swords (because François dressed as monk and opened the gates of Monaco's castle). Rainier held the citadel of Monaco for four years before departing on April 10, 1301. In 1304 he was appointed Admiral of France after winning the Battle of Zierikzee.
Francesco Grimaldi (François, in French), called il Malizia ("the malicious"), was the Genoese leader of the Guelphs who captured the Rock of Monaco on the night of 8 January 1297. He was the son of Guglielmo Grimaldi by his wife Giacobina or Giacoba, a Genoese noble.
Dressed as a Franciscan monk, Francesco was greeted at the gates of Monaco's castle, only then to seize the castle with his cousin Rainier I, Lord of Cagnes, and a group of men behind him. The event is commemorated on the Monegasque coat of arms, on which the supporters are two monks armed with swords. He held the citadel of Monaco for four years before being chased out by the Genoese. The battle over "the rock" was taken over by his kinsmen. Francesco thus failed to establish Grimaldi's rule over Monaco, but was the first to attempt to do so.
He was married in 1295 to Aurelia del Carretto; the marriage was childless. The modern Grimaldis are therefore not descendants of Francesco. After his death, in 1309, he was succeeded by his cousin (and stepson), Rainier I, Lord of Cagnes.
His cousin's descendants, the Grimaldi family, still rule Monaco today. Over one hundred years after the coup, the Grimaldis purchased Monaco from the crown of Aragon in 1419, and became the official and undisputed rulers of "the Rock of Monaco".