Osgoode Ward Councillor Doug Thompson said he's made up his mind, and he won't be running in October's civic election.
Thompson has represented the area for 31 years.
He was originally planning to retire from civic politics four years ago, but was persuaded to stay on.
He told CFRA his decision to retire now came after a tremendous amount of discussion with family and friends.
"It's just that period in your life where you feel that you've accomplished a lot," said Thompson. "I'm very proud of things that we've accomplished in Osgoode ward and in the city and it's time for - I believe - someone new to come forward. It was a very difficult decision, I'll tell you that."
The former teacher and principal said his ward is in great shape now, and the city is doing well, so now is the time to move on to other things.
He did say that he would be happy to help his successor get accustomed to his or her new role.
Four candidates have already filed their papers to contest the election in Osgoode.