Councillor Leigh Bramall has resigned from his role as deputy leader of Sheffield Council.
The Labour politician is leaving to return to a career in communications and will take up a position at a company based in the city.
He is also standing down from his role as councillor for Southey, a position he has held since 2004, which is expected to trigger a by-election.
He said: "I have been privileged to have the opportunity to serve Sheffield, working to ensure we are creating jobs, growth and investment opportunities.
"I am incredibly proud of what we have achieved, in the past year we have seen a number of very high profile businesses coming to the city, new developments being built and investors choosing to put their money into Sheffield.
"Sheffield is a special city and has many unique attributes with much to offer, this can be seen as we grow to become the country’s centre of Advanced Manufacturing and as the Outdoor City."
Coun Bramall added: "After being in the cabinet for six years and a councillor for 13 years, I have put everything into my job and love what I do.
"I remain 100 per cent committed to the work of the Labour council. But I have to put my family first and now is the right time for me to move on.
"I am moving to a fantastic Sheffield company and feel this is a great opportunity for me to start a new chapter in my professional career which also allows me to stay in Sheffield, the city that I love.
"I would especially like to thank the people of Southey who I have represented for nearly 13 years. It has been an honour to serve the community, working with some fantastic people who make a real difference for the area."
Coun Bramall has served in the cabinet for nearly six years since May 2011 and as deputy leader of the council for two years since 2015.
During this time he has led the business and economy portfolio and has worked on a number of key projects including the development of Sheffield’s Advanced Manufacturing Innovation District.
Councillor Julie Dore, leader of Sheffield Council, said: "Leigh has thrived in the business and economy portfolio where he has made a real difference in driving forward some of the city’s key economic ambitions such as the Innovation District, the city centre and Outdoor City project. He is passionate and committed to Sheffield, it has been a pleasure working with him over the past 13 years.
"He has been dedicated to serving the people of Sheffield as deputy leader of the council and given his all to the job. This inevitably takes its toll on your personal life and I completely understand and respect the decision he has made. I wish him all the best for his future career.”