French fashion designer Sonia Rykiel in 2008. (Thibault Camus/AP)

Sonia Rykiel, the flame-haired French designer once dubbed the “queen of knitwear” whose relaxed sweaters in berry-colored stripes and eye-popping motifs came to symbolize the new era of fashion freedom in the 1960s, died Thursday at her home in Paris. She was 86.

Her daughter, Nathalie Rykiel, managing and artistic director of the Sonia Rykiel fashion label, said the cause was complications from Parkinson’s disease.

President François Hollande’s office announced the death in a statement, praising her as “a pioneer” who “offered women freedom of movement.”

Ms. Rykiel became a fixture of Paris’s fashion scene starting in 1968 when she opened her first ready-to-wear shop on the Left Bank at a time when student riots were challenging France’s bourgeoisie establishment.

For the generation of women who came of age at the time, Ms. Rykiel, with her striking orange-red hair, helped through fashion to define an era of cultural and sexual upheaval.

French fashion designer Sonia Rykiel in 2010 posing for photographs in Paris, on the eve of the start of an exhibition of 200 of her drawings. (Francois Guillot/AFP via Getty Images)

Ms. Rykiel’s most identifiable pieces include the “poor boy” sweater — often in black with jewel-tone stripes or emblazoned with messages or graphic motifs like oversized red lips — knit tops with embroidered roses and funky, rhinestone-studded berets. She developed new techniques like inside-out stitching and no-hem finishings that embodied the freewheeling spirit of the times.

Brigitte Bardot and Audrey Hepburn were among the prominent actresses who promoted her clothing and sparked a demand.

The designer’s empire grew to include menswear and children’s lines as well as accessories, perfumes and home goods, sold in the label’s stores on four continents. Nathalie Rykiel, who as a young woman used to model her mother’s garments on the catwalk, has long helped manage the fashion house.

The business was among France’s last major family-owned labels until it was sold to a Hong Kong investment fund in 2012.

Sonia Flis was born in Paris on May 25, 1930, to Jewish parents who had emigrated from Eastern Europe. In a household headed by her industrialist father, she grew up in a prosperous and conservative home but said she was drawn to irreverent, tomboyish behavior.

“I was always getting lost, and my sisters would find me in a terrible state: dirty, covered with scratches,” she once told Architectural Digest. “I lived in trees or on my bicycle. The only clothes I liked were old clothes, always the same ones. My mother got so exasperated she would throw them out. So one day to get back at her, I marched out into the garden without a stitch on.”

She went through phases where she daydreamed of being an actress, writer and sculptor, but won an early compliment for her design prowess while working in Paris as a window dresser at a dry-goods store in her late teens.

French designer Sonia Rykiel, right, who appeared with her daughter Nathalie Rykiel, artistic director for the fashion house Rykiel, in 2007. (Charles Platiau/Reuters)

“One day,” she told Architectural Digest, “I happened to arrange some colorful scarves that I liked, and an elderly gentleman stopped to admire them. He came in, bought them all, and asked to pay his compliments to me in person. His name was Henri Matisse.”

In the early 1950s, she married Sam Rykiel, who owned a women’s clothing boutique called Laura. Motherhood — she had two children — set her on the path of fashion design. She began designing maternity outfits because she felt most maternity wear was too bulky and intended to hide the pregnancy, an idea she found offensive.

“I wanted to show the world how happy I was,” she told Newsweek. “My mother-in-law was scandalized, but my friends asked how they could find one like it.”

In the early 1960s, she was creating knit garments for her husband’s boutique, and she also created a sensation with the “poor boy” sweater, with its skintight form. It was featured on Elle magazine’s cover and made her an immediate star in the fashion world. The fashion trade paper Women’s Wear Daily soon called Ms. Rykiel the “queen of knitwear.”

She also penned several novels — including one about a dress and its various incarnations — and appeared as herself in director Robert Altman’s satirical 1994 look at the fashion industry, “Pret-a-Porter.”

In 2008, Ms. Rykiel celebrated her 40 years in business with a star-studded gala and fashion show where her fellow designers — including Giorgio Armani, Donna Karan and Karl Lagerfeld — sent out Rykiel-inspired outfits. Belgian designer Martin Margiela sent out a long red-fringed coat in homage to Ms. Rykiel’s frizzy red-orange bob.

The French government honored her years of service to fashion, making her an officer in the Legion of Honor in 2013.

Culture Minister Audrey Azoulay praised Ms. Rykiel as “a committed feminist” and “exceptional entrepreneur” who “created a style and work that endure.”

Her death comes as France is deep in a debate over what many see as a regression in women’s fashion and freedom, centered around full-body burkini swimsuits worn by some Muslim women. Some mayors have banned them, and leading politicians say they oppress women — but critics say banning burkinis is simply a new way to dictate what women wear.

Ms. Rykiel’s marriage ended in divorce. Survivors include two children.

“What pushes me forward is everything I have learned: political, social, cultural,” she told the New York Times in 1998. “I put all that into the clothes. Fashion should be a kind of bouillon de culture [a cultural broth]. To be modern is to be aware of what is going on.”