Ledbetter died of respiratory failure, her family said in a statement Sunday.
"Lilly Ledbetter passed away peacefully last night at the age of 86. She was surrounded by her family and loved ones. Our mother lived an extraordinary life," the statement read.
In the 1990s, after 19 years of working for Goodyear, Ledbetter learned she had been making thousands of dollars less each month that other - male - managers.
Ledbetter sued Goodyear in 1999 for gender discrimination. She initially won in federal court in 2003 and was awarded $3.8 million in backpay and damages. The decision was later overturned after the tire giant appealed.
The case eventually made its way to the Supreme Court in 2007, which upheld the lower court's ruling. In a 5-4 decision, the justices ruled Ledbetter should have filed suit within 180 days of the very first time Goodyear paid her less than her peers. Having missed that window, Ledbetter had no grounds to sue, according to the court.
In retirement Ledbetter became an activist and advocate for gender equity.
When Barack Obama became president the first bill he signed into law was the Lilly Ledbetter Fair Pay Act.
"That was the most awesome emotion I think that I have ever had," she told CNN in 2018. "I'll put it behind having a son and a daughter."
Obama lauded her on social media.
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"Lilly did what so many Americans before her have done: setting her sights high for herself and even higher for her children and grandchildren," he said on X. "Michelle and I are grateful for her advocacy and her friendship, and we send our love and prayers to her family and everyone who is continuing the fight that she began."
Senate Majority Leader Chuck Schumer also paid tribute on social media to Ledbetter's fight for pay equality. "My heart is with Lilly Ledbetter and her loved ones as they mourn her passing," he said. "May she rest in peace."
The AFL-CIO - The American Federation of Labor and Congress of Industrial Organizations - described her as a hero. "Lilly Ledbetter simply wanted to be paid the same as her male Goodyear coworkers - and her fight took her to the Supreme Court, Congress, and the White House to sign the Lilly Ledbetter Fair Pay Act. She was a true hero, and we send our deepest condolences to her family."
Salesforce CEO Marc Benioff said on social media that Ledbetter's simple phrase "equal pay for equal work" had changed his understanding.
"It's shocking that, as a CEO, I witnessed firsthand how wide the pay disparities were - not just in my own company, but across so many others we acquired. Lilly taught me the fight for equality starts with pay equity. There can be no true equality without it. My heart goes out to Lilly's family," Benioff wrote.
Ledbetter kept advocating for equal pay, writing a 2019 op-ed for CNN as Congress was once again set to debate the Paycheck Fairness Act, which did not and has not passed.
"(The wage gap) is the reality I feel the responsibility to share with the young women I meet across the country. While I was in their shoes decades ago, the reality of pay discrimination hasn't disappeared," she wrote. "One reason for that is our laws just aren't good enough."
Paying his respects on X, Rep. Chuy Garcia reiterated that the battle for pay equality was ongoing.
"Lilly Ledbetter fought tirelessly for equal pay for men and women. We mourn her loss and continue her fight. As long as Latinas and Black women earn from 51 to 66 cents for every dollar a white man earns, Lilly's fight is not over," Garcia wrote.
As of 2024, for every dollar a man earns, a woman is paid 84 cents, according to the National Committee on Pay Equity and the Equal Pay Today campaign. That's based on earnings data for full-time, year-round workers from the US Census in 2022, which was the most recent full-year data set available.
If part-time workers and those not employed year-round are included, the gender pay gap is worse, at 78 cents on the dollar, said Deborah Vagins, national campaign director of Equal Rights Advocates and director of Equal Pay Today, CNN reported in March.
"Lilly," a film about her life, premiered at the Hamptons Film Festival.
CNN's Vanessa Yurkevich and Jeanne Sahadi contributed to this report.
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