Ryan Nielsen (born March 20, 1979) is an American football coach who is the defensive coordinator for the Jacksonville Jaguars of the National Football League (NFL).

Nielsen played defensive tackle at USC from 1997 to 2001, where he started 30 games and garnered an All-Pac 10 honorable mention in 1999.^[1] Upon graduating from USC in 2002, he signed a contract with the Philadelphia Eagles in 2002 but did not make it past training camp. He also spent time with the Los Angeles Avengers of the Arena Football League.^[2]

Nielsen began his coaching career as a volunteer assistant at his alma mater USC in 2002. He also spent time as an administrative assistant at Idaho under former USC assistant Nick Holt. He was hired away as a graduate assistant at Ole Miss under his position coach at USC, Ed Orgeron, and was promoted to defensive line coach before the season began.^[3] He also had stints at Central Connecticut State and UT Martin before being hired at Northern Illinois in 2011 as a co-defensive coordinator.^[4] He followed Huskies head coach Dave Doeren to NC State in 2013 to serve as his defensive line coach and recruiting coordinator.^[5] He added the title of run game coordinator in 2014.