Philip Anthony Treacy OBE (born 26 May 1967) is an Irish award-winning haute couture milliner, or hat designer, who has been mostly based in London for his career, and who was described by Vogue magazine as "perhaps the greatest living milliner". In 2000, Treacy became the first milliner in eighty years to be invited to exhibit at the Paris haute couture fashion shows. He has won British Accessory Designer of the Year at the British Fashion Awards five times, and has received public honours in both Britain and Ireland. His designs have been displayed at the Victoria and Albert Museum and the Metropolitan Museum of Art.

In 1989, Treacy was discovered and then mentored by fashion editor Isabella Blow, whom Treacy described as the "biggest inspiration" on his life. Blow would wear and promote Treacy's designs at important fashion events and helped Treacy to break into some of the main fashion houses, particularly Chanel and Givenchy. Treacy is associated with celebrities such as Lady Gaga, Madonna, and Sarah Jessica Parker. He has been associated with British royalty and has designed hats for royal occasions, including the fascinator (or "pretzel hat") worn by Princess Beatrice in 2011.
Philip Anthony Treacy was born on 26 May 1967 in the small village of Ahascragh, near Ballinasloe, in County Galway in the Republic of Ireland, whose population was circa 500.Treacy says that his interest in sewing started at age five, and that his obsession with the weddings in the Catholic church across the road from his house inspired an early passion for fashion. In 1985, at age 17, Treacy moved to Dublin to study fashion at the National College of Art and Design, where he spent a six-week work experience with British milliner Stephen Jones, and graduated in 1987.In 1988, Treacy won an MA scholarship for the Fashion Design course at the Royal College of Art in London, and graduated in 1990 with first class honours.

When I was interviewed [for the Royal College of Art] I didn’t know whether to play down the hats or play up the hats, but they were thinking of setting up a hat course so I became their guinea pig. After one day there I said to my tutor Sheilagh Brown: “What should I do? Should I make hats or clothes?’ She said: ‘make hats.’ It was very practical, not a great revelation.

— Philip Treacy, Irish Independent, February 2011
In 1989, he took one of his hats to Michael Roberts, fashion editor of Tatler magazine, and his style editor Isabella Blow.Blow asked Treacy to make a hat for her wedding,and soon after in 1990, invited him to live with her and her new husband Detmar Blow, in their Belgravia home in London, where Treacy worked in their basement.Alexander McQueen, another Blow discovery, also shared her Belgravia home.

In July 2002, the Design Museum in London, hosted an exhibition of the 30 most iconic hats Treacy had designed for Blow, titled: When Philip met Isabella.The exhibition was so well received that it went on a world tour for several years and drew an attendance of circa 43,000 when shown in Dublin in 2005.In a 2011 interview, The Daily Telegraph said: "She made him famous. He made her look like an icon. When you think of the late, great Blow, you think of her in one of his creations, be it a giant disc or a replica sailing ship."

My biggest inspiration has been Isabella Blow. ... In twenty years I have met all my heroes and for me nobody has surpassed her. She was incredible. I thought there must be others like her, but there wasn't. Everyone was boring in comparison to her.

— Philip Treacy, Irish Independent, February 2011
In 1991, aged 23, Treacy got his "big break" when asked by Karl Lagerfeld to come to the Chanel showrooms in Paris for what was to be the start of a long-term working relationship;the meeting was held on the prompting of Blow.The first hat that Treacy designed for Chanel appeared on the cover of British Vogue worn by model Linda Evangelista; the hat was called Twisted Birdcage and was photographed by French fashion photographer, Patrick Demarchelier.

I was 23 and I'd just left [art] school, I didn't know whether to call him Mr. Lagerfeld or whatever. I was totally intimidated but Issie [Blow] was exactly herself. She just walked into the house of Chanel and said: "We'd like some tea please". I would design hats for Chanel for the next decade.

— Philip Treacy, Irish Independent, February 2011

Philip Treacy's boutique, 69 Elizabeth Street, Belgravia, London.
In 1991, Treacy opened his first showroom in London (pictured), and won the first of five British Accessory Designer of the Year awards.Two years later, Treacy held his first fashion show during London Fashion Week in Harvey Nichols, with Naomi Campbell, Yasmin Le Bon, Kate Moss, Christy Turlington and Stella Tennant modelling in return for keeping Treacy's hats, all of which were black.In 1994, he opened up his boutique at 69 Elizabeth Street, in Belgravia, London, next door to Isabella Blow's residence at number 67.

Treacy's first solo show in 1993 saw him debut on the fashion and celebrity radar when no fewer than five of the most famous supermodels of the era – Naomi Campbell, Yasmin Le Bon, Kate Moss, Stella Tennant, and Christy Turlington – appeared on his catwalk. Playing down his star appeal, Treacy is humble about his overnight success story. "London was in a lull then," he said. "The media went crazy when all those girls did my show, but it completely changed perceptions of the hat.

— Philip Treacy, The Sydney Morning Herald, 2007
Treacy has designed hats for Alexander McQueen (another discovery of Isabella Blow),including his 1999 white collection for Givenchy in Paris, for Karl Lagerfeld at Chanel, and for Valentino, Ralph Lauren, Donna Karan, Versace and Rifat Ozbek. In January 2000, he became the first milliner for eighty years to be invited to exhibit at the Paris shows.In November 2015, Vogue magazine ran a feature of Treacy's 20 "most awe-inspiring chapeaux" from the runways.