The company said Lynch would stay with the group to ensure a smooth transition and a successor would be announced in due course.
CEO Jean-Sebastien Jacques said in a statement Lynch had made “an outstanding contribution” since he became CFO in 2013.
Following his appointment, Lynch had to oversee a period of cost-cutting as commodity prices fell. They have since recovered and Rio Tinto has the strongest balance sheet in the industry.
Rio’s London share price closed 1.36 percent lower on Friday in line with broader selling in response to a stronger pound.
“I don’t see there’s an issue for Rio. He has presided over a tumultuous period and now Rio is at the top of the deck,” Paul Gait, analyst at Bernstein, said.
Reporting by Sanjeeban Sarkar in Bengaluru and Barbara Lewis in London; Editing by Elaine Hardcastle and Susan Thomas