Stephanie Kwolek died in a hospice, media sources said, citing her friend and former co-worker Rita Vasta, who did not give a cause of death. She was 90.
Kwolek was working for the US chemical company DuPont when she invented Kevlar.
"We are all saddened at the passing of DuPont scientist Stephanie Kwolek, a creative and determined chemist and a true pioneer for women in science," DuPont CEO Ellen Kullman said in a statement.
"She leaves a wonderful legacy of thousands of lives saved and countless injuries prevented by products made possible by her discovery."
Kwolek invented Kevlar in the 1960s in what she once called "a case of serendipity".
She was looking for a material that could be used to reinforce car tyres that was lighter weight and more fuel-efficient than the metal previously in use.
The liquid crystal polymer she created became Kevlar, which is five times stronger than steel and extremely lightweight.
Today, the fibre is used in body armour as well as sporting gear, boats, and in puncture-resistant tyres.
She once told an interviewer she was afraid to tell her managers about the properties of her discovery and conducted repeated tests.
"I didn't want to be embarrassed," she added. "When I did tell management, they didn't fool around. They immediately assigned a whole group to work on different aspects."
Kwolek was careful to take credit for only the initial discovery of the technology and always credited the work of others involved in its further development.
Born on 31 July 1923, in New Kensington, Pennsylvania, Kwolek graduated from the Carnegie Institution of Technology with a chemistry degree and was hired by DuPont a year after the end of World War II.
In 1996 she was awarded the National Medal of Technology and Innovation "for her contributions to the discovery, development and liquid crystal processing of high-performance aramid fibres which provide new products worldwide to save lives and benefit humankind".