Sybil Connolly (24 January 1921 – 6 May 1998) was a celebrated fashion designer and global icon known for her innovative use of traditional Irish textiles in haute couture. Often described as "Dublin's Dior", she achieved international repute and success, making her one of the first Irish designers to do so. She was a member of the "Big Three" Irish fashion designers (along with Irene Gilbert and Raymond Kenna/Kay Peterson), and was described by former Taoiseach (prime minister) Jack Lynch as "a national treasure."

She worked with brands such as Tiffany & Co. and Bloomingdale's. Among her fashion label's famous clients were American First Lady and style icon Jacqueline Kennedy, Elizabeth Taylor, the Rockefellers, and the Mellons. Her activities were covered in both the fashion press and the social columns of publications such as the Hollywood Reporter. Described by Bettina Ballard, the influential editor of American Vogue, as a "personable milk-skinned Irish charmer," she came to the notice of Carmel Snow, the Dalkey-born editor of Harpers Bazaar. Snow was instrumental in introducing Sybil Connolly to the American market and press.

Sybil Veronica Connolly was born on Clanllienwen Road, in Morriston, Swansea, Wales. Sybil was the eldest of two daughters of Evelyn Connolly (née Reynolds) from Wales and John Connolly, an insurance salesman from Waterford, Ireland. Her education came largely from her Welsh grandfather and private tutors. Her father died while she was a teenager, and the family moved to Waterford, where she spent two years at the local Our Lady of Mercy School, on Military Road. At seventeen her interest in clothes led her to be apprenticed to Bradley & Co., a prestigious London dressmaking company run by two Irish brothers, Jim and Comerford Bradley. Their clients included Queen Mary. Connolly would attend Buckingham Palace fittings where she was allowed to hold the pins. She returned to Ireland in 1940, where she worked for the Dublin store Richard Alan. She remained unknown to the general public, for the next thirteen years, until she replaced the French-Canadian head designer Gaston Mallet in 1953. She was invited by Jack Clarke to produce the next season's range. Here her work was spotted by American buyers. She was known already for her textiles, including the crystal pleated linen that was said to take nine yards of material for each yard of finished cloth. It is said that she received her initial training at The Grafton Academy.

Connolly's first major fashion show was held at Dunsany Castle in 1953. Photographer Richard Dormer used the house and its grounds for a shoot of Connolly's clothes and one picture – showing model Anne Gunning in a full-length red Kinsale cape and white crochet evening dress – made the cover of Life magazine in August 1953 under the heading 'Irish invade fashion world'." The show was a huge success – thanks in part to Harpers Bazaar editor Carmel Snow. It was attended by American press and buyers and Connolly’s career took off rapidly after that, especially in the United States.

Connolly capitalised on this publicity by travelling with her collection to the US later the same year, where she made another life-long friend, Eleanor Lambert, doyenne of American fashion publicists. Avedon's photographs of Connolly and her fashions also ran in Harpers Bazaar of October 1953. Connolly officially launched her couture label in 1957; she was 36.

Part of Connolly's success may be attributed to her flair for publicity. She was also a glamorous advert for her brand – a 1954 feature in Housewife magazine gushed: "this fairytale person has looks. Short curling dark hair. Eyes the brown of peat...And a model figure too". She was made part of the International Best Dressed List Hall of Fame in 1965.

As her profile continued to rise in the United States, so did her client list – with Julie Andrews and Elizabeth Taylor wearing her clothes. Notably, Jacqueline Kennedy wore a Sybil Connolly pleated linen dress when she sat for an official Aaron Shikler White House portrait in 1970. Many of her designs were sold, via private shows, to prominent social names such as Mellon, Rockefeller and Dupont family members. By the time she was profiled in the Saturday Evening Post in November 1957, three-quarters of Sybil Connolly's gross earnings (then estimated at $500,000 per annum) originate in sales to the United States. She broadened her export market via a friendship with the newspaper magnate Frank Packer, with two heavily publicised visits to Australia in October 1954 and August 1957.

In the late 1950s, she was employing around 100 women, half of them working from their own homes where they wove tweed or handmade lace.