The Councillor for Hanover and Elm Grove, Matt Follett has resigned due to moving outside of the city with his family.
A by election will be called within 35 days time excluding weekends and bank holidays.
Council leader Jason Kitcat said: "I wish Matt and his family all the very best for the future.
"I want to thank him for his hard work serving the residents of Hanover and Elm Grove ward over the past two years"
More top news
Philippa has the latest weather for the east
Philippa has the latest weather for the west
Nazanin Zaghari-Ratcliffe's five-year jail sentence is confirmed despite her husband's campaign to bring her home.