Born in the heart of Pamplona, Spain, Club Atlético Osasuna is a product of football enthusiasts' passion. The football club was formed on October 24th, 1920 with the merging of two local teams: Club Natación Pamplona and New Club. This union had one aim - to send forth a powerful representative from Pamplona into Spain’s soccer arena (source).

The team's early years were marked by struggles as they tried to find their place among Spanish football giants. In 1932 Osasuna got the boost it needed when it was promoted to La Liga for the first time (source). Despite initial struggles and several relegations back to lower tiers over the next few decades, notable early players such as Silvestre Igoa helped cement Osasuna's presence in Spanish football.

The late 1980s through mid-90s emerged as a golden era for Osasuna under manager Pedro María Zabalza. During this period, they consistently performed well in La Liga even reaching third position during the 1990-91 season (source). Key players during these successful years included Jan Urban who became an iconic figure due his prolific scoring record.

Another significant period came under coach Javier Aguirre between 2002-2006, with the team reaching Copa del Rey finals in 2005 and qualifying for UEFA Cup twice (source).

Osasuna's main rival is Real Zaragoza. The rivalry, born out of geographic proximity and competitive fixtures, has led to several intense matches known as 'Derbi del Ebro'. These matches are often filled with passion, drama, and unpredictable results making them a spectacle for fans (source).

Beyond simple competition, these derbies also serve as a symbol of regional pride between Aragon (Zaragoza) and Navarra (Osasuna), contributing significantly to the distinct identity that each club carries.

El Sadar Stadium has been Osasuna's fortress since it opened in 1967. With its unique asymmetrical architecture capable of holding over 18k spectators (source), this stadium is more than just a sports facility; it’s an emblem carrying decades of history.

The home advantage at El Sadar isn't only due to the vociferous support from their faithful but also from their playing style traditionally characterized by high intensity which thrives off the energy generated by home crowds.

Osasuna boasts a loyal and passionate fan base. Though primarily centered in Pamplona, their support stretches across Spain and beyond. Notable fan groups include ‘Indar Gorri’, known for their vocal support and vibrant displays (source).

An enduring tradition is the team wearing red shirts with navy blue shorts representing the colors of Navarra's flag. The club also keeps a strong connection with its Basque roots, often promoting players from its youth academy much to the delight of fans who love seeing local talents flourish.

1. Formation of Osasuna in 1920.
2. First promotion to La Liga in 1932.
3. Achieving third place position during 1990-91 season under Pedro María Zabalza.
4. Jan Urban becoming top scorer for Osasuna during early '90s.
5. Reaching Copa del Rey finals in 2005.
6. Qualifying for UEFA Cup twice between 2002-2006 under Javier Aguirre's leadership
7. Winning against Real Madrid at Santiago Bernabeu during the 2003-04 season (source).
8. Completion and inauguration of El Sadar Stadium in 1967.
9. Defeating arch-rival Real Zaragoza by a margin of three goals during the 'Derbi del Ebro' in February, 2011 (source). 10 Celebrating 100 years of existence in 2020.