Rio Tinto chief executive Tom Albanese resigned after the company announced a writedown of $US14 billion relating to the company's aluminium and coal-mining businesses.
Rio Tinto said he stepped down by mutual agreement with the board and has been replaced by Sam Walsh, chief executive of the mining group's iron ore business.
In a statement, chairman Jan du Plessis said the scale of the writedown was unacceptable.
The BBC reports the $US10-11 billion writedown of aluminium assets was largely related to the company's purchase of Alcan of Canada in 2007.
Rio paid $US38 billion for it shortly before the onset of the global financial crisis.
About $US3 billion of the writedown relates to Rio Tinto's coal mining operations in Mozambique.
Doug Ritchie, who led the acquisition of the Mozambique coal assets as head of the energy division, has also resigned.
Shares in the company fell more than 3% when stock markets in London opened.
The writedowns, which reflect a reduction in the value of assets, will be included in Rio Tinto's full-year results, which are due on 14 February.