The Republican-led Senate has already begun its effort to repeal President Barack Obama’s health-care law, but Democrats are not giving up their fight to keep the Affordable Care Act intact.

On Sunday, Sen. Elizabeth Warren will lead a rally at Faneuil Hall alongside Sen. Ed Markey and Boston Mayor Marty Walsh to “save health care.”

Called “Our First Stand,” the Boston rally is just one of several initiatives across the country, according to the website of Vermont senator and former presidential candidate Bernie Sanders, who is helping spearhead the effort. Health care rallies are slated for such cities as Honolulu, Chicago and Hartford, Connecticut.

Warren first announced news of the event via an email to supporters. She noted that when the Affordable Care Act was signed, “Massachusetts went all in — expanding Medicaid, setting up an insurance exchange, and working to make coverage more affordable.”

If the law is repealed, Warren said, commonwealth residents have a lot to lose.

In Massachusetts, the uninsured rate fell 36 percent since the ACA was signed into law in 2010, meaning 107,000 Bay Staters got health insurance coverage, according to the U.S. Department of Health and Human Services.

The more than 4 million residents covered through employer-sponsored health care saw benefits from ACA as well, like an end to annual and lifetime limits on their plans, free preventative care (including flu shots, cancer screenings and contraception) and a slower increase of premiums, according to an HHS report. 

“Our health care laws aren’t perfect. We need to do a lot more to bring down the costs of insurance for working families,” Warren wrote to her supporters. “But we cannot and will not allow Donald Trump and the GOP to recklessly strip away coverage for millions of people who desperately need their health care.”

Facebook event for the rally asks those interested in attending to officially register at elizabethwarren.com. The rally is scheduled from noon to 3 p.m. at Faneuil Hall on Sunday.