Oscar de la Renta, a renowned American fashion designer famed for his glamorous red-carpet gowns and smart suits for ladies who lunch, died Monday evening at the age of 82, a spokeswoman for his fashion house confirmed.

Mr. de la Renta died just a few weeks after he named a new designer to replace him at his eponymous brand.

Possibly the U.S.'s most noted fashion designer, Mr. de la Renta managed to stay relevant for more than six decades. Even in his final days, he was the go-to designer for celebrity brides and socialites who flocked to his rich, ever-feminine designs, which radiated wealth and power. He dressed Amal Alamuddin in September for her wedding to George Clooney.

First lady Michelle Obama recently wore one of his dresses, after having seemed to snub him for years. Mr. de la Renta, designer of countless looks for previous first ladies from Betty Ford to Laura Bush, had openly chafed at the seeming oversight, which caused speculation that Mrs. Obama preferred emerging designers.

The response to the designer's death in the fashion industry was immediate, as he had served as a father to American fashion. The Savannah College of Art and Design said it would fly flags at half-staff, according to a spokesman.

During Paris Fashion Week in September, the house of de la Renta announced that Peter Copping, designer of Nina Ricci, will take the design reins.

Mr. de la Renta was born in the Dominican Republic, then got his start in the 1950s as an assistant to Spanish designer Cristóbal Balenciaga. Mr. Balenciaga was noted for his daring approach to volume, which certainly trained Mr. de la Renta's eye for proportion. But the American designer--who later designed for Lanvin and Balmain--kept versatility as his mark. He designed for every era's jet set in his lifetime--from Jacqueline Kennedy Onassis, Babe Paley and Zsa Zsa Gabor, to Beyoncé, Sarah Jessica Parker and Penélope Cruz.

His collections in recent years flew from florals to geometric prints, and from voluminous gowns to body-conscious day looks and suits suitable for chairwomen of the board--as though he was suggesting that there was no design feat he couldn't accomplish.

Ever-tanned, he began as a modernist, but in recent years sometimes struggled to include designs to appeal to young women while catering to his well-heeled, but elder clientele.

His outsize influence on high-amp fashion came to a head in 2006 when four attendees at the Kennedy Center Honors arrived for a White House reception in the same red, $8,500 Oscar de la Renta dress, including then-first lady Laura Bush. Mrs. Bush went upstairs and changed.

Elizabeth Holmes contributed to this article.

Write to Christina Binkley at christina.binkley@wsj.com

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