"I no longer believe the chairman role is the right professional fit for me," The Wall Street Journal said Ross wrote in an e-mail to employees Friday. "For that reason, I have made the very difficult decision to step down as chairman of The Walt Disney Studios, effective today."
Ross did not indicate what his future plans are.
The newspaper reported Ross' announcement comes shortly after Disney admitted it expects to lose $200 million on the recent box-office dud "John Carter," which cost more than $250 million to make and $100 million to market.
Disney Chairman and Chief Executive Robert Iger thanked Ross in a separate statement for "his countless contributions throughout his entire career at Disney." Iger also said he expects Ross "will have tremendous success in whatever he chooses to do next."
Ross previously ran the Disney Channel for more than a decade, overseeing a successful programming slate that included the wildly popular "Hannah Montana."
Notable deaths of 2014 [PHOTOS]
Meg Ryan, Kiernan Shipka to star in 'Fan Girl'