The first ladies of the principality were out in force, with Charlotte Casiraghi, Princess Caroline's daughter, competing in the amateur class watched by her mother and Charlene Wittstock - her uncle Prince Albert's companion.
Despite the heat, all three beauties lived up to their reputation for effortless chic, looking fresh and cool in what seems to be a Monegasque summer staple, close-fitting white trousers.
Charlotte, a keen equestrian, was last seen flying over jumps in expert style during the Valencia stop of the tour, which Athina Onassis also attended in support of her husband Alvaro 'Doda' De Miranda.
It's the first time the fearless royal has been back in the saddle following a car crash involving her and her boyfriend of two years Alex Dellal. Though she looked fit and on form, there was evidence of the mishap in the strapping on her left hand.