Bank of America's CEO Ken Lewis, the embattled head of the nation's biggest bank, told the board he plans to step down by the end of the year.
Lewis wasn't asked to step down and the decision was not the result of any regulatory action, sources told CNBC. No successor has been named yet.
The Charlotte, North Carolina-based Bank of America's board will continue evaluating potential successors, a company announcement said.
BofA stock moved higher in after-hours trading. Click here for after-hours quote.
Lewis, 62, ran Bank of America for nearly a decade, succeeding his mentor Hugh McColl in 2001.
After being named to the top spot, he proceeded to build one of the nation's largest financial services companies through aggressive acquisitions.
But in the last year, Lewis was the subject of rising political criticism, along with federal and state investigations into the bank's acquisition of Merrill Lynch in late 2008 and early 2009.
He had previously announced hopes of retiring after the bank repaid $45 billion in government assistance, or when he hit the company's mandatory retirement age of 65.
BofA's shareholders voted in April to oust Lewis as chairman after months of mounting criticism of his stewardship of the bank.
"It's a good thing for the company to make a clean break and move forward," Walter Todd, portfolio manager at Greenwood Capital Associates, told Reuters. "Ken Lewis has been overly targeted in terms of how things played out. But the fact is, perception is reality in these situations."
But not everything saw the resignation as a positive.
"For Bank of America this is bad," well-known banking analyst Dick Bove of Rochdale Securities told CNBC. "Lewis was a phenomenally good CEO, made a series of very strong positive decisions, including buying Merrill Lynch. I think it is a definite loss to Bank of America."
Bove said he thought the leading candidate to succeed Lewis would be Brian Moynihan, currently head of BofA's consumer and small-business banking.
Other possible successors include Thomas Montag, head of Global Markets; Barbara DeSoer, Bank of America Home Loans; Sallie Krawcheck, president of Global Wealth; Joe Price, CFO, and Greg Curl, chief risk officer.
Two board members are also possible contenders: Charles Gifford, 66, Bank of Boston's former CEO, and William Boardman, 67, retired Banc One executive.
—Reuters contributed to this story