Glossop Labour councillor Dave Wilcox is standing down as chair of the county council because of ill health.
Cllr Wilcox, who represents Hadfield, Tintwistle and Gamesley on the authority, was appointed as chair in May 2013.
He said: “After more than 30 years as a county councillor it was a great honour to be elected as Chair of Derbyshire County Council and I regret that ill-health has meant that in recent months I have not been able to fulfil my responsibilities in that office.
“For this reason, I have decided to step down and would like to take this opportunity to wish my successor all the best as they take up this role.
“I will continue to be a county councillor representing communities in my local area and look forward to carrying on my service to local people in this way.”
Councillor Wilcox also announced he would be standing down as Chair of the Board of the Local Government Think Tank LGIU, which he has led for the last ten years, and is resigning from his position as a vice chairman of the County Councils Network.
Meanwhile, Derbyshire County Council Conservative Group last week elected a new leader after current leader Andrew Lewer MBE was elected as an MEP.
Cllr Barry Lewis will be supported by re-elected deputy leader Cllr Simon Spencer and new group secretary Cllr Jocelyn Street, of Chapel-en-le-Frith, who will take a Shadow Cabinet role.
Cllr Lewis said: “It is a great honour and humbling to be elected as Group Leader for Derbyshire County Conservatives, especially following on from a skilful leader like Andrew.”