Club Atlético Osasuna ([ˈkluβ atˈletiko osaˈsuna], Osasuna Athletic Club), or simply Osasuna, is a Spanish professional football club in Pamplona, Navarre. Founded on 24 October 1920, the club currently plays in La Liga, holding home games at the 23,576-capacity El Sadar Stadium. The team's regular home kit is a red shirt with navy blue shorts. Osasuna is one of four professional Spanish clubs to be owned by its members with an elected president.

Osasuna is the sole Navarrese club to have played in La Liga. Although the club has never won a national trophy it reached the Copa del Rey final in 2005. The club’s best league finishes were fourth in 1990–91 and 2005–06.

"Los Rojillos" is the club nickname, meaning "The Little Reds". The word "osasuna" means "health" in Basque, used in a sense of "strength" or "vigour", which makes Osasuna the only team in La Liga with a Basque name. For different reasons, rivalries exist between Osasuna and Real Zaragoza, Real Madrid, and some Basque clubs, particularly Athletic Bilbao.

Osasuna has a cantera which has produced several successful players similar to other clubs in the greater Basque region.

The club was founded on 24 October 1920 and its name, Osasuna, was chosen by Benjamín Andoian Martínez. When Spanish football became professional in 1928, Osasuna was placed in the third division, gaining promotion to the Segunda División after the 1931–32 season by winning the playoff against Nacional de Madrid. They made it to La Liga three seasons later. That same season, they reached the semi-finals of the Copa del Rey and lost to Sevilla. The next season , Osasuna reached the semi-finals again, this time losing to Barcelona over two legs, despite grabbing a victory in the first leg.