Costelloe became one of the best-known names in British and Irish fashion and was personal designer to the late Diana, the Princess of Wales.
His family issued a statement on Saturday saying they were “deeply saddened to announce the passing of Paul Costelloe following a short illness”.
They added: “He was surrounded by his wife and seven children and passed peacefully in London.”
He was born in Dublin, where his father ran a successful company making raincoats.
After studying at the Grafton Academy of Fashion Design, he moved to Paris, where he took a course at the Chambre Syndicale de la Haute Couture in Paris.
He set up his own label in 1979, Paul Costelloe Collections, and presented collections at London Fashion Week, as well as in Paris, Milan and New York.
In 1983, he was appointed personal designer to Diana, Princess of Wales, a collaboration which continued until she died in 1997.
Costelloe often used traditional Irish fabrics and textiles in his designs, including Irish linen and tweed.
He collaborated with Dunnes Stores and was the closing designer for the inaugural Ireland Fashion Week in October this year.
He was criticised in 1998 when he said that Irish women lacked style.
“Irish women have difficulty with style because it’s not in their inner nature… like the Italians,” he said at the time
However, during an interview with Irish broadcaster RTÉ this year, he said he felt that Ireland was more European than years ago.
Taoiseach (Irish PM) Micheál Martin said he was “very saddened to learn of the passing of Paul Costelloe”.
“An icon of design, Paul elevated Irish fashion to the global stage,” he said
Tánaiste (deputy PM) Simon Harris said Costelloe had “led a remarkable life”.
Harris added, “He built a hugely successful business through incredible talent, discipline, and an unwavering commitment to quality.
“He leaves behind a body of work that shaped modern Irish fashion and will continue to shape it in the years to come. He will be greatly missed and warmly remembered.”
