Gourlay said in a statement he was off to "pursue new business challenges" after five years in his current role.
Chelsea said in a statement: "Ron's efforts have helped the club to achieve its position as one of the leading football clubs in the world."
Chelsea won the Champions League for the first time in 2012, but they were also widely criticised for their handling of the John Terry affair when the FA found their skipper guilty of racially abusing Anton Ferdinand, then of Queens Park Rangers, in October 2011.
They also endured an uneasy second half of the 2012-13 season when Rafa Benitez took charge of the club, an appointment hugely unpopular with the majority of their fans, although he did bring them silverware by winning the Europa League.
Gourlay leaves the club with the team at the top of the Premier League and a day after they beat Maribor 6-0 in the Champions League, their record victory in the competition.
Image: Ron Gourlay with John Terry
Photograph: Jamie McDonald/Getty Images
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