Ryan Wallace Zimmerman (born September 28, 1984 in Washington, North Carolina) is a baseball third baseman with the Washington Nationals of Major League Baseball. A 6-foot 3-inch player from the University of Virginia and Kellam High School, Zimmerman has been a member of the Nationals since his debut on September 1, 2005. He was given the nickname Magnum Z.I. by broadcaster Rob Dibble, and Pete Franchise by fellow player Nyjer Morgan in the 2009 season.

Zimmerman's mother Cheryl was diagnosed with multiple sclerosis in 1995, and has been in a wheelchair since 2000. Zimmerman has cited his mother's condition as a substantial formative influence on his development, saying that it forced him to grow up and assume responsibilities at an earlier age than most children. He also founded the ziMS Foundation.

A three-year starter third baseman for the Virginia Cavaliers in the Atlantic Coast Conference, Ryan Zimmerman started in all 174 games he appeared in, and his collegiate career statistics include 250 hits, 140 RBI, 128 runs, 47 doubles, seven triples and nine home runs. He was successful on 32 of 39 stolen base attempts. His career totals are among the top ten in Virginia statistical categories for doubles (5th), hits (6th) and RBI (7th). Ryan established the school record of hits in a season with 90 in 2004, breaking his own record with 92 in 2005.