The palace announced Wednesday that Charlotte Casiraghi gave birth to Raphael a day earlier. The baby's father is French actor and comedian Gad Elmaleh.
Members of Monaco's royal family are followed like celebrities in France. The wedding two years ago between ruling Prince Albert and South African Charlene Wittstock had the same red carpet glamor of Prince William's marriage to Kate Middleton.
But the palace has kept the birth announcement low key. Charlotte, who is not herself a princess, is the second child of Caroline and the late Italian businessman Stephano Casiraghi.
Caroline is Albert's older sister, daughter of the late Prince Rainier and the late American actress Grace Kelly.