Business tycoon and former politician Bernard Tapie and his wife Dominique Tapie were attacked by robbers in their mansion near Paris, in the early hours of Sunday morning.
The couple were tied up with electrical cord and beaten by a gang of four men.
Ms Tapie managed to free herself and made her way to a neighbour's home, from where she called the police.
She needed hospital treatment for several blows to the face.
"She is doing well," grandson Rodolphe Tapie said.
The robbers "pulled her by the hair because they wanted to know where the treasure was," said Combs-La-Ville mayor Guy Geoffroy.
"But of course there was no treasure, and the fact that they didn't find one made the violence only worse."
Police are treating Sunday's incident at the Tapies' home in Combs-la-Ville near Paris as a violent robbery and kidnapping.
Mr Tapie, 78, was hit on the head with a club, prosecutor Beatrice Angelelli said, but he declined to be taken for medical care.
The burglars broke into the Tapie home, a vast estate known as the Moulin de Breuil, through a first-floor window, undetected by the guards.
They made off with two watches, including a Rolex, earrings, bracelets and a ring, according to a source close to the investigation.
Mr Tapie was a Socialist minister who rose from humble beginnings to build a sporting and media empire, but later ran into a string of legal problems.
He would regularly flaunt his wealth, including the buying of a 72-metre yacht and a football club, Olympique de Marseille, which won the French championship while he was owner.
He was briefly minister for urban affairs in Francois Mitterand's government in 1992.
Mr Tapie was found guilty in a series of cases for corruption, tax fraud and misuse of corporate assets, went to prison for five months and was stripped of the right to stand in any election in France.
After his release from prison in 1997, he added showbiz to his various activities, trying his hand at acting, singing and hosting radio and TV shows.
In 2012 he also became a media boss, taking over southern French daily La Provence and other newspapers.