The six could face life in jail after prosecutors charged them with kidnapping 76-year-old Jacqueline Veyrac, who owns the five-star Grand Hôtel on the Croisette at Cannes and La Réserve restaurant in Nice.
She was found by a passerby, bound and gagged and lashed to the floor of a van.
Her rescuer noticed that a number plate was loose, revealing another one underneath.
She had sustained several injuries in attempting to escape, according to Nice prosecutor Jean-Michel Prêtre.
Restaurateur harboured grudge
The restaurateur, known as Giuseppe S, harboured a grudge against Veyrac, who owns La Réserve restaurant, which he ran between 2007 and 2009 when it went into liquidation.
The kidnapping was a bid to recover the money he lost, according to investors, although they earlier said no ransom demand had been made.
Former paparazzi Luc G, also known as Tintin, is accused of fitting a tracking device to Veyrac's SUV, while a former British special forces soldier who was sleeping on the streets, is alleged to have provided surveillance.
The three other people charged are believed to be gang members who grabbed Veyrac outside her home in central Nice.
Veyrac, who co-owns the Grand Hôtel with her son, was the victim of another kidnapping attempt three years ago and investigators are seeking to establish whether the two events are connected.