Florestan I, Prince of Monaco was Prince of Monaco and Duke of Valentinois from 2 October 1841 until his death. He was born Tancrède Florestan Roger Louis Grimaldi the second son of Prince Honoré IV and Louise d'Aumont Mazarin and succeeded to the throne on the death of his brother, Honoré V.
As unprepared as Florestan was for the affairs of the Principality, his ascendance to power upon the death of his brother was largely welcomed by the populace. The prince attempted to meet local demands for democratic reforms and offered two constitutions to the local population, but these were rejected, particularly by the people of Menton, who were offered something better by King Charles Albert of Sardinia. When the Prince and Princess of Monaco saw that their efforts were doomed to failure, they handed over power to their son Charles (later Prince Charles III). This was, however, too little, too late. Encouraged by the French Revolution of 1848, the towns of Menton and Roquebrune revolted and declared themselves independent. Worse, the King of Sardinia garrisoned Menton, Florestan was dethroned, arrested, and imprisoned. Florestan was restored to the throne in 1849, but Menton and Roquebrune were lost forever.