Now, Ms. Fraser will be tasked with improving returns that trail industry leader J.P. Morgan Chase and using the bank's global network in a world that's seeing more nationalism and trade barriers. "We completed our transformation from the financial crisis and emerged a simpler, safer and stronger institution," Mr. Corbat said in the statement. "There is always more to do and I believe the time is right for my successor to lead Citi through this next stage of progress." Ms. Fraser, a 53-year-old Scot, joined Citigroup in 2004 after a decade as a McKinsey & Co. consultant. Her promotion last year came after she was viewed as a potential candidate for CEO jobs at other banks, including Wells Fargo & Co. She will join Citi's board immediately and take on the CEO role once Mr. Corbat retires, the New York-based bank said in a statement Thursday. Under Mr. Corbat, Citigroup has become a slimmer organization with just two main businesses: the institutional clients group and the global consumer bank.