The high-speed prince was driving his Audi on the A6 motorway which links Paris and Lyon. Police caught up with him close to the town of Mâcon, around 40 miles north of Lyon.
According to Le Parisien newspaper, police immobilized the 27 year old’s car and handed him a five month suspension. The nephew of prince Albert of Monaco will also need to appear in front of magistrates in Mâcon.
Casiraghi, who is a favourite of celebrity magazines, is second in line to the throne of the tiny principality, after his mother. He was listed as one of the 20 Hottest Royals by Forbes magazine in 2008.
The prince was just six years old when his father, Stefano Casiraghi, died in a boating accident in 1990.
He is currently studying for a masters degree at the university of Barcelona.