The miniskirt (often hyphenated as mini-skirt) is a skirt with a hemline well above the knees (generally 20 cm—about 8 inches—or more above knee level). The mini was the defining fashion symbol of "Swinging London" in the 1960s.
A minidress is a dress with hemline above knees.
After World War I, hemlines had risen rapidly. By the mid-1920s, dresses worn by young "flappers" were often above the knee which was only allowed by the abandonment of the constraining corsetry of Victorian and Edwardian times. The miniskirt's existence in the 1960s was generally credited to the fashion designer Mary Quant, who was inspired by the Mini automobile, although the French designer André Courrèges is also often cited as its inventor (the French referred to it as la mini-jupe), and there is disagreement as to who invented it first. Some give the credit to Helen Rose, who made some miniskirts for actress Anne Francis in the 1956 science fiction movie, Forbidden Planet.
Recently, Marit Allen, a Vogue "Young Ideas" editor at the time, has stated that "John Bates, in particular, has always been completely unappreciated for his contribution to the innovation and creativity he brought to the London design scene." He bared the midriff, used transparent vinyl and, Marit Allen asserts, was responsible for "the raising of the hemline. It was John Bates, rather than Mary Quant or Courrèges, who was responsible for the miniskirt." Bates' costumes and accessories for Diana Rigg, as Emma Peel in the ABC-TV series, The Avengers, from 1965--7, helped to define "Mod style". As The Avengers' filmed episodes were made several months before screening, Avengers producer Brian Clemens confirmed in interviews that the miniskirt designed by Bates was a "gamble", since they did not know if it would catch on in public or be seen as a fashion failure by the time the episodes aired. However, Emma Peel's fashions were accepted by the public and even spawned a line of replicas of her clothes for public sale. Another more "immediate" proponent of the miniskirt on television was Cathy McGowan, who introduced the weekly British rock music show, Ready Steady Go! (1964-6).
 Mary Quant and Jean Shrimpton
Mary Quant ran a popular clothes shop in the Kings Road, Chelsea, London called Bazaar, from which she sold her own designs. In the late 1950s she began experimenting with shorter skirts, which resulted in the miniskirt in 1965—one of the defining fashions of the decade.
Owing to Quant's position in the heart of fashionable "Swinging London", the miniskirt was able to spread beyond a simple street fashion into a major international trend. Its acceptance was greatly boosted by Jean Shrimpton's wearing a short white shift dress, made by Colin Rolfe, on 30 October 1965 at Derby Day, first day of the annual Melbourne Cup Carnival in Australia, where it caused a sensation. According to Shrimpton, who claimed that the brevity of the skirt was due mainly to Rolfe's having insufficient material, the ensuing controversy was as much as anything to do with her having dispensed with a hat and gloves, seen as the essential accessories in such conservative society.
The miniskirt was further popularised by André Courrèges, who developed it separately and incorporated it into his Mod look, for spring/summer 1965. His miniskirts were less body-hugging, and worn with the white "Courrèges boots" that became a trademark. By introducing the miniskirt into the haute couture of the fashion industry, Courrèges gave it a greater degree of respectability than might otherwise have been expected of a street fashion.
The miniskirt was followed up in the late 1960s by the even shorter micro skirt, which has been referred to derogatorily as a belt or pelmet. Upper garments, such as rugby shirts, were sometimes adapted as mini-dresses. Tights or panty-hose became highly fashionable, in place of stockings, specifically because the rise in hemlines meant that stocking tops would be visible. Mary Quant cited this development in defence of the miniskirt: "In European countries where they ban mini-skirts in the streets and say they're an invitation to rape, they don't understand about stocking tights underneath".