Dial is resigning for personal reasons and will become a senior adviser, the bank said. She will be succeeded by Manuel Medina-Mora, who will also continue in his role as chairman and chief executive for Citi Mexico and Latin America.
Citigroup Chief Executive Vikram Pandit hired Dial in 2008 to head North American consumer banking and global consumer strategy. Dial had previously worked at Lloyds TSB, where she was credited with reviving the bank's retail operations.
Lloyds investors viewed her as so crucial to retail banking that reports of her departure pushed the bank's shares down 2 percent.
But many employees inside Citigroup see her as having been less successful there. Citigroup's North American regional consumer banking operations, along with many other businesses at Citigroup and across Wall Street, have experienced declining revenue since the beginning of 2008, and profitability has been spotty.
An outside review of Citigroup's management, demanded by U.S. regulators in the aftermath of the financial crisis, raised questions about Dial's managerial skills, according to press reports in October.
Company spokesman Jon Diat declined to comment beyond the bank's press statement.
Dial worked at Wells Fargo & Co
Citigroup's North American regional banking operations had revenue of $1.7 billion and earnings of $163 million in the 2009 third quarter. (Reporting by Dan Wilchins in New York and Joe Rauch in Charlotte, N.C.; editing by John Wallace)