Bettencourt leaving a fashion show in 2001 with daughter Francoise.
"We all had a deep admiration for Liliane Bettencourt who has always watched over L'Oreal, the company and its employees, and who was very attached to its success and development", Agon wrote.
"My mother left peacefully", her daughter Francoise Bettencourt-Meyers said.
In October 2011, a court ruled Ms Bettencourt was suffering from a form of dementia, and awarded the daughter control over her mother's wealth and income - then estimated at $26 billion and including about 33 per cent of L'Oreal.
In a statement to the BBC, L'Oreal chairman and CEO Jean-Paul Agon confirmed her death and offered condolences.
Patrice de Maistre, who managed Bettencourt's vast fortune, was sentenced to 30 months in prison, 12 of which were suspended, and a fine of 250,000 euros.
Sarkozy's former campaign treasurer, Eric Woerth, was acquitted on charges of "abuse of weakness" and taking donations from Bettencourt during the 2007 presidential election campaign.
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Bettencourt was the only child of L'Oreal founder Eugene Schueller, she inherited his fortune following his death in 1957.
Liliane, who had lost her mother when she was five years old, adored her father, whom she liked to say "taught me the meaning of hard work".
She was, however, no stranger to controversy.
Her husband, who died in 2007, had been a member of a French fascist group during the war but sought forgiveness from the Jewish community in its aftermath.
During those years, neither Mr Schueller nor Mr Bettencourt were able to shake accusations of pro-Nazi sympathies and anti-Semitism despite their close association with Francois Mitterrand, the former socialist president.
Famed for its "Because you're worth it" advertising campaign, L'Oreal is France's fourth-largest listed firm. Liliane Bettencourt was the heiress to the L'Oréal fortune.
L'Oreal also owns The Body Shop.