Ryan Nelsen (born October 18, 1977 in Christchurch) is a soccer player from New Zealand, who currently plays defense for Blackburn Rovers of the Premiership.

Nelsen came to United States of America to play for Greensboro College in North Carolina in 1997. After spending two years at Greensboro and leading the team to the NCAA Division III Final Four, Nelsen moved to Stanford University, where he played his final two years of college soccer. At Stanford, Nelsen was voted team MVP in his first year, and named an NSCAA All-American in his senior year, while playing as a defensive midfielder.

Nelsen was drafted 4th overall in the 2001 MLS SuperDraft by D.C. United, with whom he has spent four years in Major League Soccer. After emerging as a starter in 2002, Nelsen was named team captain in 2003, replacing Marco Etcheverry in that role, as well as winning the team's Defender of the Year Award and being named to the league's Best XI. He was named to the Best XI again in 2004. In four years in MLS, Nelsen has scored seven goals and added five assists.

Nelsen has also been a vital player for the New Zealand national team. He was signed by Blackburn after the 2004 MLS season.