Insider sources told Bloomberg that Ms Landsman, who was appointed to the role in August 2009, has tendered her resignation.
Reacting to the news, Thomas Noyes, who ran Citigroup's international online banking operations between 2006 and 2007 and is now a consultant at Starpoint Partners, said: "If they can't keep people like Liza, things aren't going to get done.
"She was very well-respected."
In her brief time in the position, Citi Mobile launched a variety of applications for the iPhone, while also bringing out Citi Shopper, a service which allows users to compare prices and provide directions to nearby retail outlets.
Last month, insiders told Bloomberg that the bank is considering moving its proprietary traders to its hedge fund unit in order to comply with the regulations laid out in the Dodd-Frank Act.
By Gary Cooper