(Oscar de la Renta takes a bow with models Karlie Kloss and Daria Strokous at New York fashion week. AP)
The designer rose to prominence in the 1960s when then-First Lady Jackie Kennedy wore his garments and he went on to launch his own fashion label.
Former First Lady Hilary Clinton also used to regularly wear his designs, as did Laura Bush and Nancy Reagan, and earlier this month Michelle Obama, US President Barack Obama's wife, wore one of his garments to an event.
The Dominican Republic-born designer dressed several stars throughout a highly successful career, including Cameron Diaz, Nicole Kidman, Penelope Cruz and Audrey Hepburn.
Just last month, one of his latest commissions was Amal's wedding dress and he appeared in the pages of Vogue magazine with her as she posed for pictures trying on the beautiful custom-made French lace gown.
Lawyer Amal later praised Oscar for creating the outfit for her big day.
She said: "George and I wanted a wedding that was romantic and elegant, and I can't imagine anyone more able than Oscar to capture this mood in a dress.
"Meeting him made the design process all the more magical, as he is so warm and such a gentleman."
Oscar also admitted he was fully aware of the importance of the garment and hoped he had created exactly what Amal wanted.
He said: "It's the most important dress in the life of a woman.
"Any girl from any walk of life dreams of that special dress, and I try to make that dream a reality for her.
"Amal and I looked at a lot of evening dresses and wedding dresses together, and we discussed what she liked. That gave me the idea of what she wanted."
Oscar is survived by his wife Annette and adopted son Moises.
Celebrities have taken to social media to express their condolences.
My all-time favorite designer has passed away. Oscar, it was an honor to wear your creations and to… http://t.co/AOfPZbHg1i
— Taylor Swift (@taylorswift13) October 21, 2014
What a sad day for the fashion industry. An icon is gone. RIP Oscar de la Renta ??
— Nicky Hilton (@NickyHilton) October 21, 2014
Truly saddened by the loss of one of the greatest fashion icons of all time. Oscar de la Renta will be greatly missed.
— Ivanka Trump (@IvankaTrump) October 21, 2014
Sad to hear of the death of #OscardelaRenta. What a remarkable life and career, and a kind and generous man.
— Anderson Cooper (@andersoncooper) October 21, 2014
In shock. I saved an oscar de la renta dress for 4 yrs to wear to a special occasion #TheAngelBall & he passes away. #riposcar
— Bethenny Frankel (@Bethenny) October 21, 2014