The day before Linda Wetzel closed on her retirement home in Southport, N.C., in 2012 — a cozy place where she could open the windows at night and catch an ocean breeze — the bank making the loan surprised her with a fee she hadn’t expected. Ms. Wetzel scoured her mortgage paperwork and couldn’t find the charge disclosed anywhere.

Ms. Wetzel made the payment and then filed an online complaint with the Consumer Financial Protection Bureau. The bank quickly opened an investigation, and a month later, it sent her a $5,600 check.

“My first thought was ‘thank you.’ I was in tears,” she recalled. “That money was a year or two of savings on my mortgage. It was my little nest egg.”

Ms. Wetzel’s refund is a tiny piece of the work the bureau has done since it was created in 2011. It has clawed back $21 billion for consumers. It slashed overdraft fees, reformed the student loan servicing market, transformed mortgage lending rules and forced banks and money transmitters to compensate fraud victims.

It may no longer be able to carry out that work.

President Trump on Friday appointed Russell Vought, who was confirmed a day earlier to lead the Office of Management and Budget, as the agency’s acting director. Mr. Vought was an author of Project 2025, a conservative blueprint for upending the federal government that called for significant changes, including abolishing the consumer bureau.

In less than 36 hours, Mr. Vought threw the agency into chaos. On Saturday, he ordered the bureau’s 1,700 employees to stop nearly all their work and announced plans to cut off the agency’s funding. Then on Sunday, he closed the bureau’s headquarters for the coming week. Workers who tried to retrieve their laptops from the office were turned away, employees said.

The bureau “has been a woke & weaponized agency against disfavored industries and individuals for a long time,” Mr. Vought wrote Sunday on X. “This must end.”

Created by Congress in the aftermath of the housing crisis that set off the Great Recession, the consumer bureau became one of Wall Street’s most feared regulators, with the power to issue new rules — and penalize companies for breaking them — around mortgages, credit cards, student loans, credit reporting and other areas that affect the financial lives of millions of Americans.

The bureau’s actions made it a lightning rod for criticism from banks and Republican lawmakers — and put it squarely in the Trump administration’s cross hairs.

The agency’s foes have long called for its elimination, which only Congress has the power to do. Elon Musk, the billionaire leader of a government efficiency team that has created havoc throughout the federal government, posted “CFPB RIP” on his social media platform X on Friday. A few hours earlier, his associates had gained access to the consumer bureau’s headquarters and computer systems.

The National Treasury Employees Union, which represents the bureau’s employees, filed a lawsuit against Mr. Vought on Sunday night. Granting Mr. Musk’s team access to employee records violated the Privacy Act, the 1974 law regulating how the government handles individuals’ personal information, the union said in its complaint, which was filed in federal court in Washington.

Agency workers fear their employment data could be used for online harassment or “to blackmail, threaten or intimidate them,” the complaint said. Workers are also concerned about disclosure of their personal health or financial details, the union added.

The union filed a second lawsuit against the acting director over his efforts to freeze the agency’s work. Mr. Vought’s orders illegally infringe, the union said, on “Congress’s authority to set and fund the missions” of the consumer bureau.

Representatives of the consumer bureau and the budget office did not respond to requests for comment.

During the first Trump administration, when Republicans controlled both chambers of Congress, lawmakers failed to amass enough votes to abolish the agency. Some have indicated that they would like to try again. Senator Bill Hagerty, a Tennessee Republican who serves on the Senate Banking Committee, called the bureau a “rogue agency” on Sunday on the CBS News program “Face the Nation.”

“It’s been basically a reckless agency that’s been allowed to go way beyond any mandate that I think was originally intended,” Mr. Hagerty said. “It’s time to rein it in.”

Senator Elizabeth Warren, Democrat of Massachusetts, who fought for the agency’s creation and who describes herself as its “mom” on her X biography, has spent the last decade battling attempts to dismantle the consumer bureau.

“President Trump campaigned on helping working families, but Russ Vought just told Wall Street that it’s open season to scam families,” she said Sunday in a written statement. “What Vought is doing is illegal and dangerous, and we will fight back.”

Many of the agency’s actions have directly affected Americans’ pocketbooks. Its rules overhauled the mortgage market, curbing the kinds of subprime loans that set off the housing crisis. Pressure from the bureau led major banks to reduce or eliminate their overdraft fees, and a recently finalized rule would cap most of those fees at $5.

The agency recently adopted rules to eliminate medical debt from credit reports and limit most credit card late fees to $8 or less per month, but lawsuits have delayed those rules from taking effect.

“It’s striking to me that people’s economic dissatisfaction created the Consumer Financial Protection Bureau, and people’s economic dissatisfaction created Trump,” said Shayak Sarkar, a law professor at University of California, Davis.

Mr. Trump’s team has given priority to attacks on specific agencies — like U.S. Agency for International Development and the consumer bureau — that serve vulnerable populations, Mr. Sarkar said, while throwing “a lot of federal support and cheering” at agencies like Immigration Customs and Enforcement, which has intensified its immigration crackdowns.

While the bureau cannot be shuttered without congressional action, its director has the power to radically alter its approach. During Mr. Trump’s first term, he appointed Mick Mulvaney — then the director of the budget office Mr. Vought now leads — as the bureau’s acting director. Mr. Mulvaney called the agency a “joke” in “a sick, sad kind of way” and sharply curtailed its enforcement actions and rule making work.

The agency’s powers have swung like a pendulum. It moved aggressively when Democrats held the White House but pulled back during Mr. Trump’s first term. Mr. Mulvaney and his Trump-appointed successor, Kathleen Kraninger, put the bureau into a kind of hibernation, gutting rules that would have wiped out much of the payday lending market and slashing the bureau’s enforcement actions.

But several current agency employees, who spoke confidentially for fear of retribution, said Mr. Vought’s order on Saturday stretched beyond what occurred during the last Trump administration.

His instruction to “cease all supervision and examination activity” caused particular alarm. While other federal agencies — including the Federal Deposit Insurance Corporation, Federal Reserve and Office of the Comptroller of the Currency — also oversee banks, the consumer bureau is the sole regulator for nonbank lenders. Those companies hold a large share of the $13 trillion mortgage market.

Mr. Vought also said he intended to cut off the consumer bureau’s funding, which comes directly from the Federal Reserve, outside the usual congressional appropriations process. The agency’s budget for the 2025 fiscal year calls for around $800 million in annual spending, and the Fed transferred $245 million to the bureau in January to fulfill its latest request.

Mr. Vought wrote on X that he had told the Fed that the bureau would not be taking its next funding draw “because it is not ‘reasonably necessary’ to carry out its duties.”

Adam Levitin, a professor at Georgetown Law who specializes in financial regulation, said on Sunday that Mr. Vought’s orders might be illegal. Some of the federal laws that govern the consumer bureau order it to supervise specific entities, and that work does not appear to be discretionary, he said.

The acting director “has the ability to seriously hobble the C.F.P.B. through a bunch of slow bleeds, but he’s trying to skip all the necessary steps and just go for an immediate death blow,” Mr. Levitin said. “He may not have the legal ability to actually do that, but I’m not sure how much that’s going to matter. A lot of the way the Trump administration has been dealing with regulatory agencies is just kind of a blitzkrieg tactic, where a key component is creating fear, uncertainty and chaos.”

A rally on Saturday outside the bureau’s headquarters, organized by its staff union, drew a few hundred participants. A Maryland resident, who asked that her name be withheld for fear of retribution from Mr. Trump’s allies, attended with her husband, a federal worker, to support the agency’s employees.

“I don’t think people understand what the C.F.P.B. does,” she said. “The administration said they’re closing it because of fraud, but the bureau’s literal job is to protect people from fraud and junk fees and predatory lenders.”

Ms. Wetzel, the retiree who used her $5,600 refund to replace the floors in her new home, said the quick action on her complaint made her feel empowered.

“It was such a relief to have the government saying what the bank did was wrong, that this is not the rule of law,” she said.