As part of his role, Ryan will serve as an advisor to owner Jim Crane, general manager Jeff Luhnow and Reid Ryan. Ryan, who is Major League Baseball's all-time strikeout leader, has more than 45 seasons of experience as a player and an executive.
"We're extremely pleased to have Nolan as part of our organization," Crane said in a statement. "We will use his experience, expertise and knowledge to improve the Astros in all areas. He will be an integral part of our management team. Nolan wants to be a part of our success moving forward."
Ryan, citing a desire to spend more time on his ranch and with his family, stepped down as the chief executive officer of the Rangers at the end of October. He met with the Astros last month and was mulling an offer to rejoin the organization.
"I'm very excited to be back with the Astros," he said in a statement. "I'm happy to assist Jim, Jeff and Reid in any way I can. The Astros have a solid foundation with a strong farm system. I think the future is bright for Houston and I'm looking forward to my involvement."
Ryan grew up just south of Houston in Alvin, Texas, and pitched nine of his 27 years with the Astros (1980-88), before finishing his playing career in Arlington. He worked for former owner Drayton McLane in an advisory role from 2004 to 2008 and was hired by former Rangers owner Tom Hicks as club president Feb. 6, 2008.
Ryan later joined with an ownership group put together by Chuck Greenberg that submitted the highest bid in a bankruptcy auction Aug. 12, 2010. When Greenberg was forced out in March 2011, Ryan added the title of CEO.
"Nolan Ryan's experience and insights will help us on the baseball side -- both in terms of decision-making and in maximizing the productivity of our players," Luhnow said. "I'm fortunate as a general manager to get advice and guidance from great former players and Astros -- Craig Biggio, Roger Clemens and now Nolan Ryan."
After retiring as a player following the 1993 season, Ryan worked in the Rangers' front office before returning to the Astros as special assistant to the general manager in February 2004. In his first two seasons back with Houston, the Astros enjoyed plenty of success, falling one game shy of winning the National League pennant in '04 before capturing the pennant in '05 to become the first team from Texas to play in a World Series.
"The opportunity to work with my father is very special," Reid Ryan said. "He's had success in baseball on many levels and will be a great addition to our organization. He will be an extremely valuable asset to us."
Ryan won 324 games, establishing all-time records in strikeouts (5,714) and no-hitters with seven (and also threw 12 one-hitters). He helped the Astros reach the playoffs in 1980 and '86 and was inducted in the National Baseball Hall of Fame in 1999.