In what the team had called a retirement, Ryan said Thursday that he is resigning as chief executive of the Rangers in a move effective at the end of this month. He is also selling his ownership stake in the team to co-chairmen Ray Davis and Bob Simpson.
"It closes a chapter of my life in baseball," Ryan said. "I feel like it's time for me to move on to other things. It's been a decision that weighed on me heavily, but I feel like it's the right decision. ... At this point and time, it's the correct thing for me to do."
Asked about the difference in the team announcing that he was retiring and him calling it a resignation, the 66-year-old Ryan paused and then said he wouldn't be the CEO of another major league team and called this perhaps the "final chapter" of his storied career in baseball.
Ryan's older son, Reid, became president of the Houston Astros earlier this year. Nolan Ryan dismissed any speculation that he's leaving the Rangers to join his son and another of the teams he pitched for and worked for in the past.
The move takes effect Oct. 31.
Ryan became the 10th president of the Rangers in February 2008 when he was hired by former owner Tom Hicks. Ryan added the title of CEO three years later. He was also part of the ownership group that acquired the team in August 2010, months before its first World Series.
Ryan's departure comes less than a year after ownership gave general manager Jon Daniels and chief operating officer Rick George new presidential titles and took the president's title from Ryan.
Davis insisted the change in Ryan's title earlier this year was just that.
"From a corporation standpoint, Nolan's authority didn't change at all," Davis said. "On all major decisions on baseball, Nolan made all final decisions."
Ryan said the title change wasn't a factor in his decision.
"I don't look at it from that perspective," Ryan said. "I just look at it from where I am in life and what I want to do going forward and that's what really drove my decision."
George left in July to become the athletic director at the University of Colorado. Daniels attended the news conference at Rangers Ballpark, but left without speaking to reporters.
Davis said the ownership group is disappointed with Ryan's decision but understands it. Simpson said he tried to talk Ryan out of leaving.
"You don't wake up one day and make a decision of this magnitude," Ryan said. "It was something I've been thinking about on and off for a while now. Just felt like it was probably time for me to move on."
Ryan said he planned to go home and enjoy getting back out to his ranch "and doing things I haven't done for six years now. ... I don't know what a year from now might bring. This may be the final chapter of my baseball career."
Texas made its only two World Series appearances during Ryan's six seasons in the front office. The Rangers have averaged more than 90 wins the past five seasons, though they missed the playoffs this year after losing an AL wild-card tiebreaker game to Tampa Bay.
"During times of significant change for the franchise, Nolan has been a constant — accessible, dedicated and an icon to his fellow Texans who love our game," Commissioner Bud Selig said. "Nolan's unique perspective as a legendary player and an accomplished executive has been invaluable to the Rangers franchise."
Ryan's name has been synonymous with the Rangers for decades.
The major league strikeout king with 5,714 spent the last five seasons of his playing days in a Rangers uniform, getting his 300th victory, throwing the last two of his record seven no-hitters and getting his 5,000th strikeout. He retired as player after the 1993 season.
His No. 34 jersey is the only one worn by a Rangers player to be retired, and there is a statue of the pitcher at Rangers Ballpark. He is the only player in the Hall of Fame whose bust is topped by a Texas cap.
"As his son, I am extremely proud of what he has accomplished as both a player and as a front office executive. He was an integral part of all three of the World Series appearances by Texas teams, in 2005 with the Astros and in 2010-11 with the Rangers," Reid Ryan said in a statement.
"He has always treated the game with dignity and respect and has appreciated those that make our game great: the fans, players and employees," he said.
The co-chairmen said there are no immediate plans to announce a new CEO. Rob Matwick, who's currently executive vice-president of ballpark and event operations, will take on more responsibilities with the help of others who have also been shifted into new roles.
As for representing the Rangers in MLB business, Davis said he'd "be the control person for the next two or three years, and Bob and I will rotate that title."
AP Sports Writer Stephen Hawkins contributed to this report.