Born Juan Carlos Antonio Galliano in Gibraltar to Spanish parents, he moved to London as a child and attended Wilson's School in Wallington. In 1984, he graduated in fashion design from St. Martin's School of Arts, with a collection inspired by the French Revolution called Les Incroyables, that received positive reviews and was bought in its entirity and sold in the London fashion boutique Browns. Following that, he started his own label under his name and began his career as a fashion designer. He was awarded British Designer of the Year in 1987, 1994 and 1995. In 1997, he shared the award with Alexander McQueen, his successor at Givenchy.

In the 1990s, Galliano relocated to Paris in search of financial backing and a strong client base. In 1995, he was appointed as the designer of Givenchy by Bernard Arnault owner of luxury goods congolmerate LVMH, thus becoming the first British designer to head a French haute couture house. Less than two years later, on October 14, 1996, LVMH moved Galliano to Christian Dior. His first couture show for Dior coincided with the label's 50th anniversary, on January 20, 1997.

He has been quoted as identifying his love of theatre and femininity as central to his creations -- "my role is to seduce" he has said. Galliano has reputedly cited Charlize Theron as a muse and has been creating couture dresses for her to wear to red carpet events such as the 2006 Academy Awards and the 2005 Golden Globes. She is also part of the ad campaign for Dior's "J'Adore" perfume, while Riley Keough, granddaughter of Elvis Presley, fronts his "Miss Dior Cherie" perfume, and Kate Moss, in photographs by Nick Knight, his ready-to-wear campaigns. Cate Blanchett and Nicole Kidman have also worn dresses created by him to the Academy Awards in the past.

Currently, between his own label and Dior, Galliano produces six couture and ready-to-wear collections a year and a new mid-season range under his own name.

Galliano says he follows a rigorous exercise regime which sees him rise at 6am each morning to complete a gruelling, 40-minute aerobic session with his personal trainer, before embarking on a 10-minute stretch, doing 150 push-ups and a six-mile jog along the banks of the Seine River. "Working flat out, it was a necessary step to take," he once said. "It helps to concentrate the mind and I find that I have so much more energy and focus." In 2000, he said that he also had found his inspiration for the couture collection of boho-meets-hobo chic he unveiled that January during his jogging sessions, when running past the homeless people lining the river. He added that he hoped to expose the pure decadence of couture by "turning it inside out".