Founded in 1920 it currently plays in La Liga, holding home games at the 19,553-capacity El Sadar Stadium. The team's home kit is red shirt, navy blue shorts, black socks with red back, whereas the away one is navy blue shirt, orange shorts and navy blue socks.
The word Osasuna means "health" in Basque (used in a sense of "strength", "vigour").
After a stellar 2005–06 domestic campaign, Osasuna made history by finishing in fourth place – tied for best ever – synonymous with the chance of qualifying for the UEFA Champions League in the following season through play-off matches. This achievement was made even more dramatic by the suspense that was maintained until the last day of the championship in which Osasuna and Sevilla FC were both vying for the fourth place – both teams eventually ended the season with the same number of points but Osasuna got through due to their head-to-head record; However, Osasuna didn't make it to the Champions League group phase, as they were eliminated by Hamburger SV in the third qualifying round, leaving the Navarrese to vie in the UEFA Cup for the fifth time in their history.
Osasuna were drawn in Group D of the 2006–07 UEFA Cup along with Parma FC, RC Lens, OB Odense and SC Heerenveen. The club qualified for the knock-out stage, finishing second in their group, and were drawn against FC Girondins de Bordeaux, who had dropped into the UEFA Cup following an unsuccessful Champions League campaign; the Spaniards progressed 1–0 on aggregate, drawing 0–0 away before winning 1–0 in Pamplona through an extra time winner by Javad Nekounam.
Next up were Glasgow Rangers, and Osasuna again progressed, following a 1–1 draw in Scotland and a 1–0 win at home. They were drawn against German side Bayer 04 Leverkusen in the quarter-finals. Regarded as severe underdogs, they not only progressed to the semifinals but did so in style (a 3–0 away win had virtually sealed the tie, but the Rojillos also won the second leg, 1–0); in the last-four round the club was drawn against holders and fellow Spanish side Sevilla, eventually losing 1–2 on aggregate after a 1–0 home win.
In the following two seasons, Osasuna struggled heavily in the league: in 2008–09, it only avoided relegation in the final day: being in 18th place and going into the final matchday, at home to Real Madrid, they fell behind 0–1, but came back with two goals (the decider courtesy of Juanfran, a Merengue youth graduate) to remain in the top flight.
Osasuna's women's team currently plays in Segunda División's Group 2, finishing in third position in 2009–10. In the 2010s, some controversies arose over the organization's management of the team: in March 2011, eleven players left the team accusing the executives of sexism, lack of interest and poor training conditions, and, in May of the following year, outgoing chairman Patxi Izco declared women's football as unsightly and unsuitable for women.