In a statement released by Yost, the 65-year-old skipper announced his retirement after nine seasons leading the club. The retirement is effective Sunday after the team's regular-season finale against the Minnesota Twins.
"With the development of our young players and our returning veterans, I feel and hope the worst is behind us in this rebuilding phase of our organization," Yost said in the statement. "My plan all along was to get us through the rough times then turn it over to a new manager to bring us the rest of the way.
"I've thoroughly enjoyed my time here as your manager and will never forget the good and the hard times we had together as an organization and a fan base. I will never forget the fact that you fans supported us through it all. Kansas City will always have a special place in my heart, and I look forward to rooting the Royals on to their next World Championship very soon."
The announcement came on an off-day for the Royals, who lost to the Twins on Sunday. The 12-8 defeat pushed the club's record to 57-100, marking Kansas City's second straight season with at least 100 losses.
Yost, who has been serving as manager on a year-to-year contract, will step away as the Royals' career wins leader with 744 to date. He is the only manager in team history to guide the Royals to back-to-back World Series appearances, losing to the San Francisco Giants in seven games during the 2014 campaign and beating the New York Mets in five games the next year.
Yost and Royals general manager Dayton Moore are expected to conduct a press conference Tuesday to address reporters.