Rey Juan Carlos University (RJC University) (Spanish: Universidad Rey Juan Carlos, URJC) is a Spanish public research university located in the southern area of the Community of Madrid (Spain), with five campuses at Móstoles, Alcorcón, Vicálvaro, Aranjuez and Fuenlabrada.

It is named after former king Juan Carlos I of Spain and has the Latin motto Non nova, sed nove ("Not new things, but in a new way"). It was established in 1996 by the government of the Community of Madrid.

With 44,916 students, it is the second-biggest public university in the Community of Madrid, behind the historical Universidad Complutense. URJC is one of eight universities in the Community of Madrid, and it is the second-newest university in the autonomous community.