Coates became chairman 12 years ago and enjoyed success when Lou Macari led Stoke back to the First Division in 1993, but he has also been the subject of numerous demonstrations from supporters who claim the club have not invested enough money in the team.
Coates insisted it was his decision to leave, despite repeated calls by supporters for him to be replaced. "The decision to go was entirely mine. I've made it because I think a change would be good for the club and for me," he said.
"Being chairman involves a lot of hard work and pressures. I never intended to do it forever, contrary to what some people might have thought."
It is not yet known who will take over from Coates at the Britannia Stadium, but he will stay on the board and his successor is expected to be announced in the next few days. The club is also facing managerial turmoil with Chris Kamara at the centre of a tug-of-war between Stoke and Portsmouth.
Kamara, sacked by Bradford City last week, is favourite to replace Chic Bates at Stoke. However, Portsmouth have also sounded out Kamara about becoming their next manager after the sacking of Terry Fenwick.
Kamara is due for talks with Pompey today, but Stoke may now increase the intensity of their interest in him or lose out. Bates is ready to stand down at Stoke and could even team up with Kamara, which may go some way to appeasing their fans.