Missoni's death was confirmed by the president of the Lombardy region, Attilio Fontana, who praised the Missoni brand's "famous multicoloured textures".
"The passing of Rosita Missoni, a Lombard stylist and entrepreneur known throughout the world, saddens us. A great loss for Italy, Lombardy and for the province of Varese where she was born and lived," Fontana wrote in a statement.
Missoni helped develop the signature look of the eponymous brand, lauded by influential fashion journalist Bernadine Morris in 1977 as one that had "elevated knitting to an art form".
Long a fixture of Italian fashion, Missoni in 1953 co-founded the line that became instantly recognisable for its distinctive zigzag patterns and unabashed use of colour.
Together with husband Ottavio -- who died in 2013 at age 92 -- they began working on knits from the basement of their new home after marrying in 1953.
The daughter of shawl manufacturers from northern Italy, Rosita was born in 1931 in the Lombard town of Golasecca.
She was on a study trip to London when she met her husband, known as Tai, who was competing in the 400 metres hurdles at the Olympic Games.
Ottavio Missoni had already begun a business applying knitting to sportswear, making tracksuits with zippers, an innovation that allowed an athletes to put on his trousers without removing his trainers.
The idea attracted Italy's athletics federation, which adopted it for the London Olympics in 1948.
In their new home in Gallarate, northwest of Milan, the pair soon moved from tracksuits to sweaters.
"When I got married, four sewing machines arrived with my husband," Rosita Missoni told AFP in a 2016 interview.
A big break came five years later where department store Rinascente in Milan ordered hundreds of close-fitting striped dresses bearing the Missoni label for the first time.
Their fame was assured in 1967 after being invited to present their collection at the Pitti Palace in Florence.
Missoni had asked the models to remove their white bras because they could be seen under the blouses. But under the spotlights of the catwalks, the lightweight clothes became even more see-through.
While not invited the following year, the reputation of the Missoni label grew.
In 1997, Rosita handed over the reins of the fashion house to her daughter Angela, while devoting herself to the label's home line, Missoni Home.
