Caroline Kerr has confirmed the news in the last couple of hours.
She took over the role from Liz Green at the start of the Covid-19 pandemic in spring last year.
Councillor Caroline Kerr, Liberal Democrat Councillor for Canbury, said, "It is with a heavy heart that I am resigning as Leader of Kingston Council. It has been a huge honour to lead the Royal Borough and this is not a decision I have taken lightly. I will stay in post until my successor has been selected.
"I am extremely proud of the work of the Liberal Democrat Council in serving the people of Kingston, particularly in these most challenging times. Together we have supported Kingston’s residents and our local NHS through the pandemic, we are building the first council homes in a generation and we are investing in two new leisure centres which will serve everyone in the borough for the next 50 years. All whilst we have turned around the council finances after the Conservatives had left Kingston on the edge of bankruptcy under their watch.
"I became Leader as Covid 19 struck. I was able to draw on my professional experience of helping organisations deal with crisis to support the council through the pandemic. Although Covid is still a threat, the worst of the emergency appears to be over and I feel it is now time for new leadership to take the borough and the Liberal Democrat group on the next phase of its journey.
"These last 18 months have been a time of unprecedented challenge. It has taken a toll on us all. Like many, I have spent some time taking stock, reflecting on my commitments to the Council, my family and to the residents of Canbury. After much consideration and having led the Council through this challenging period, I have decided that I must stand down as Leader.
"I’d like to thank staff at Kingston Council, our partner organisations and elected members for their support and commitment to serving local residents. I will stay on as leader until a new leader is chosen. I will continue to represent the residents of Canbury to the best of my ability and to campaign against cuts to peak train services at Kingston station."
Cllr Margaret Thompson, Mayor of Kingston from May 2019-April 2021, said, "I would like to thank Cllr Kerr for her excellent and diligent leadership for the past nineteen months. Cllr Kerr has led the Liberal Democrat group during the most challenging period the Council has ever had to face, using her skills of crisis management and forward thinking to ensure that the residents of Kingston were as well supported as possible during the pandemic. We look forward to moving on with a new leader to take us into the future and wish Cllr Kerr all the best after this difficult period."