Founded in 1920, the club currently plays in La Liga, holding home games at the 19,800-capacity El Sadar Stadium. The team tends to play in a red shirt with navy blue shorts, whereas the away kit differs from season to season.
“Los Rojillos” is the club nickname, meaning “The Reds”. The word “osasuna” means “health” in Basque, used in a sense of “strength” or “vigour”. For different reasons, rivalries exist between Osasuna and Real Zaragoza, Real Madrid, and some Basque clubs, particularly Athletic Bilbao.
Osasuna had varied success following those seasons, but struggled again from 2012 to 2014, being relegated to the second division after an 18th-place finish in 2013–14. In the 2014-15 season, the club managed to rank one position above the relegation zone. A managerial change resulted in substantial improvement, and Osasuna won the final match of the regular 2015–16 season 0–5 away to Oviedo, finishing sixth in the table and qualifying for promotion playoffs and. They subsequently won all the playoff games – against Gimnàstic de Tarragona in the semi-final and Girona in the final – to achieve promotion once again to La Liga. Osasuna finished 2016–17 in 19th position, resulting in relegation. They could only manage 8th in their first campaign back in the second tier.
On Monday 20 May 2019, Osasuna achieved promotion back to La Liga after Granada’s victory over Albacete, mathematically ensuring a promotion place with three matches left in the season. On 31 May, they defeated Córdoba to finish as 2018–19 Segunda División champions.