A company spokeswoman, confirming the death, provided no details on the cause, but Mr. Dumas had had Parkinson’s disease for several years.

Mr. Dumas assumed leadership of Hermès in 1978, at a low point in the company’s fortunes. Founded in 1837 by Thierry Hermès as a harness maker, it had diversified to include clothing, jewelry and accessories by the 1920s. Although its Kelly bags and signature square scarves were fashion must-haves, the company was languishing, hobbled by its fusty image.

With a free, sometimes audacious hand, Mr. Dumas began shaking things up. He hired exciting new designers, extended the company’s lines, expanded internationally and invested in companies like the glassware maker Saint-Louis, the tableware company Puiforcat and the fashion house of Jean Paul Gaultier.

In a characteristic bit of opportunism, he turned a chance encounter with the English actress Jane Birkin into one of Hermès’s biggest successes. Seated next to Ms. Birkin on a Paris-to-London flight in 1984, he began asking her about her tattered straw handbag and then invited her to work with Hermès to develop a new handbag design.