Known universally by his first name, Valentino died on Monday at his residence in Rome surrounded by his loved ones, according to a joint statement shared on his and his foundation's Instagram page.
Giancarlo Giammetti, Valentino's partner in business and life, posted his picture on Instagram captioned "forever".
Valentino transformed high fashion after co-founding his eponymous luxury brand in the 60s alongside Giammetti and became known for his shade of "Valentino Red" as well as his signature use of bows, ruffles, and lace.
He went on to become synonymous with dressing high society with Diana, Princess of Wales, actress Elizabeth Taylor and former US first lady Jackie Kennedy among his clients.
Tributes have since poured in from leading figures from across industries, including fashion designer Donatella Versace.
"Today, we lost a true maestro who will forever be remembered for his art. My thoughts go to Giancarlo (Giammetti) who never left his side for all these years. He will never be forgotten."
Paltrow, who wore a Valentino gown for her wedding to Brad Falchuk in 2018 as well as a bright pink long-sleeved dress at the 2013 Met Gala said the news felt like the "end of an era".
"I was so lucky to know and love Valentino - to know the real man, in private," she said on Instagram.
"The man who was in love with beauty, his family, his muses, his friends. His dogs, his gardens, and a good Hollywood story.
"This feels like the end of an era. He will be deeply missed by me and all who loved him. Rest in peace, Vava."
Sex and the City star Sarah Jessica Parker also paid tribute to the designer, praising him and the legacy he leaves behind.
"For your extraordinary talent, your decadent generosity and your love of all things beautiful, we are all more fortunate for the grand gestures you shared with the world," she said.
Model Cindy Crawford said in a post on Instagram that she was "heartbroken" and described Valentino as a "true master of his craft".
"I will always be grateful for the years I had the privilege of working closely with him."
The luxury brand also paid tribute to their co-founder in a post on Instagram, praising his "unique style and innate elegance".
"We share with heartfelt sympathy the grief of his loved ones, and we remain committed to preserving and elevating the valued creative, cultural, and human heritage he entrusted to us, upon which Maison Valentino is founded," the statement said.
"His life was a beacon in the ceaseless pursuit of beauty, and guided by that same beauty, we will continue to honour his memory with our deepest devotion."
Throughout his illustrious career, Valentino dressed a number of high-status clients including the Princess of Monaco, Grace Kelly, along with fellow actresses Audrey Hepburn and Sophia Loren.
His dresses became red carpet favourites for Hollywood stars, with gowns worn by Sharon Stone, Anne Hathaway and notably Julia Roberts, who wore a black and white vintage Valentino gown to the 2001 Oscars where she won the best actress award for legal drama Erin Brockovich.
Cate Blanchett also wore a buttermilk yellow Valentino gown at the 2005 Oscars where she took home the best supporting actress award for her role in The Aviator.
Others who have also paid tribute to the fashion designer include models Coco Rocha who said "fashion lost another giant" and Carla Bruni who said it was an honour and a privilege knowing Valentino and modelling for him.
Meanwhile Euphoria actor and Valentino ambassador Colman Domingo thanked the designer for "inspiring so many to be beautiful" in a post on Instagram, with American fashion designer Zac Posen describing him as "truly one of a kind".
Italian Prime Minister Giorgia Meloni was among the first to pay tribute to the couturier, describing him in a post on X as the "undisputed master of style and elegance" adding that he was the "eternal symbol of Italian high fashion".
"Today Italy loses a legend, but his legacy will continue to inspire generations. Thank you for everything."
Valentino's work and influence on the fashion industry was recognised in 2006 when he received the Legion d'honneur, France's highest honour.
The designer announced his retirement in 2007, two months after hosting a lavish three-day celebration in Rome to mark 45 years in the fashion industry which drew a huge celebrity turnout.
Valentino will lie in state at the foundation's headquarters on Piazza Mignanelli on Wednesday and Thursday before a funeral service on Friday at the Basilica of Saint Mary of the Angels and Martyrs in Rome's Piazza della Repubblica.
with Reuters
