L'Oreal heiress Liliane Bettencourt, 88, is to be placed under the guardianship of members of her family.
A French judge made the ruling based on concerns about Mrs Bettencourt's declining mental health.
The family are reportedly concerned about her health and management of her fortune, estimated at 16bn euros (£13bn: $20bn) by Forbes magazine.
Mrs Bettencourt's lawyer said the decision was "profoundly disappointing".
Jean-Rene Farthouat said he would appeal against the court's ruling, which will remain in place pending the appeals process.
Liliane Bettencourt is estranged from her daughter, Francoise Bettencourt-Meyers, who, along with two grandsons, will now control her wealth and property.
Another grandson was named as her personal guardian.
Mrs Bettencourt is on L'Oreal's board of directors, but the court's decision is expected to have little impact on the running of the cosmetics giant.
The Bettencourt mother and daughter have been at the centre of a very public feud over the fate of France's third-largest family fortune.
Mrs Bettencourt-Meyers has argued that her mother is mentally unfit to manage her wealth.
In an interview published in the Journal du Dimanche on Sunday, Liliane Bettencourt threatened to leave France if her daughter succeeded in having her placed her under her guardianship.
"If it's that, I will go abroad. If my daughter looks after me I would feel stifled. If it's her, I will leave," she said.