Long-standing Royston councillor Graham Kyte has stepped after 15 years of service.
Coun Kyte said it was his intention to resign rather than stand for re-election last year but because fellow ward councillor Tracey Cheetham was ill, he was asked to continue.
Now Tracey has recovered he has decided to resign and a by-election will be held on October 10 to find a replacement.
"There are some younger people in the local party who would like to offer themselves as councillors. I would now like to hand over to a younger pair of hands," Coun Kyte said.
He said there have been some minuses and some plusses during his time as councillor.
Highlights include the lifelong learning centre, improvements to homes on Midland Road, the Westmeads extra care facility, the new park pavilion and the restoration of Rabbit Ings, he said.
But the loss of Royston fire station, Oakwood care home and the building of the new supermarket off Midland Road have been negatives during his tenure.
Coun Kyte said he decided to be a councillor after taking early retirement.
"I wanted to see if I could put something back into the community that had been very good to me."
But despite no longer being a councillor, he says he will continue to be active politically as chairman of the Royston ward Labour Party, hoping to persuade the national party to put forward policies that people in Royston will want to vote for.
"It has been a privilege to represent the people of Royston for the past 15 years and I am very grateful to all those who have supported me at five successful elections," he said.
"I hope they will now support the new Labour Party candidate in the same way."