UK Sport chief executive Liz Nicholl has announced she will step down from the role in the summer of 2019.
Nicholl, who first joined UK Sport in 1999 – just two years after the organisation was established – said she was leaving the role to "focus on family and other interests".
Nicholl spent her first 10 years at UK Sport as director of elite sport, before becoming chief operating officer in 2009.
She was then appointed CEO in September 2010 after John Steele stepped down to become CEO of the Rugby Football Union.
During her nine-year tenure as CEO, Team GB has achieved historic performances at successive Olympic Games.
At London 2012, the team achieved 65 medals and finished third in the medal table. This was followed by an unprecedented second place in the medal table at Rio with 67 medals.
“It’s been a huge privilege to work with so many committed and talented athletes, coaches, leaders, partners and colleagues during my time at UK Sport," Nicholl said.
"I have shared a very special journey with everyone that has been part of our very successful high-performance system over the past 20 years.
"Our athletes are undoubtedly among the very best prepared and supported in the world and I am confident that we can continue to build on the successes of recent Games.
"The UK’s international reputation as an ambitious, innovative host of major and mega events delivered to quality standards is at an all-time high and enables us to showcase our successful British athletes.
"The UK is also leading the way in addressing sports governance and integrity challenges and we continue to contribute positively to sports policy and development around the world.
“None of this would have been possible without the fantastic support and that we have received from National Lottery players and from our government. Thank you for supporting us on this journey. I hope we have made you very proud.
“This really is the best job in sport and I have enjoyed every minute of it. I am confident that it will attract some great applicants and my successor will find British sport in a good position to realise our vision of inspiring the nation in Tokyo and beyond.
In a statement, UK Sport said the search for a successor would begin imminently to allow for a "smooth transition and handover for Tokyo 2020 Games".
