Dixons Carphone boss Sebastian James is leaving the firm to join the parent company of high street chemist Boots.
He will be replaced at the electrical and mobile retailer by Alex Baldock as chief executive, who currently heads up online retailer Shop Direct, with brands including Littlewoods and Very.
James has been at Dixons since 2008 and intends to step down in April.
Ian Livingston, chairman of Dixons Carphone, said:
Seb has made an outstanding contribution to both the creation and success of Dixons Carphone. It is a much stronger company today than when he became CEO of Dixons Retail in 2012 with revenue, profit and customer satisfaction all substantially higher.
The group is now the market leader in eight countries.
He added that Baldock came with an "outstanding track record in leading large, complex consumer-facing businesses", delivering five consecutive years of "record financial performance, with strongly rising sales and an almost tenfold increase in profits".
The news comes just ahead of the firm's results for over the Christmas period, expected on Tuesday 23 January.
First-half profits at Dixons Carphone, which employs over 42,000 people in nine countries, slumped after it reported that people were holding onto their mobiles for longer, and not upgrading them enough.
It said in December it planned to shake up the way it sells smartphones, "repositioning" that part of the firm to "deliver a simpler, less capital-intensive business".
That followed a profit warning back in August.
James' exit at Dixons Carphone comes after the departure of the boss of its software business, Graham Stapleton, who joins Halfords.
In a statement, James said it had been "an enormous privilege to lead this business" and said he was "very sad to leave", but was "very proud of the profound transformation that we have seen in Dixons Carphone".