WASHINGTON—President Biden will nominate Michael Barr, a former Treasury Department official, to serve as the Federal Reserve’s top banking regulator, the White House said, after Mr. Biden’s first pick for the job withdrew in the face of opposition from Republicans and a key Democratic senator.

If confirmed, Mr. Barr would serve as the Fed’s vice chairman for supervision, charged with overseeing the largest U.S. financial firms including JPMorgan Chase & Co., Bank of America Corp. and Citigroup Inc. A key architect of the 2010 Dodd-Frank postcrisis financial regulatory overhaul and the Consumer Financial Protection Bureau, Mr. Barr would likely bring close scrutiny to bank mergers and rules for lending in low-income neighborhoods.