Born in Kent, Quant studied illustration at Goldsmith's College before taking a job with a couture milliner. In October 1955, she teamed up with her husband Alexander Plunkett Greene, and an accountant Archie McNair, to open a clothes shop on the Kings Road in London called Bazaar.
Following the positive reaction to a pair of "mad house pyjamas" designed for the opening, and dissatisfied with the variety of clothes available to her, Quant decided to make her own range of clothing. Initially working solo, she was soon employing a handful of machinists, producing unusual clothes she considered to be fun.
Her skirts had been getting shorter since about 1958 - a development she considered to be practical and liberating, allowing women the ability to run for a bus. The miniskirt, for which she is arguably most famous, became one of the defining fashions of the 1960s. The miniskirt was developed separately by Andre Courrèges, and there is disagreement as to who came up with the idea first.
In addition to the miniskirt, Quant is often credited with inventing the coloured and patterned tights that tended to accompany the garment, although these are also attributed to Cristobal Balenciaga.
Irrespective of whether she invented these items, Quant was one of their major popularisers, largely thanks to the fact that Bazaar was a popular haunt for the fashionable Chelsea Set of "Swinging London". By 1961, Quant had opened a second Bazaar in Knightsbridge and by 1963 she was exporting to the USA. To keep up with demand, Quant went into mass-production, setting up the Ginger Group.
Quant's popularity was at its peak in the mid 1960s, during which time she produced the dangerously short micro-mini skirt, "paint-box" make-up, and plastic raincoats. She was described as being the leading fashion force outside Paris.
In 2000, she resigned as director of Mary Quant Ltd., her cosmetics company, after a Japanese buy-out. There are over 200 Mary Quant Colour shops in Japan, where Quant fashions continue to enjoy some popularity.