Football was introduced to Austria–Hungary at the end of the 19^th century, when returning students from university towns were spreading the game throughout the country. The first recorded football match was played in Ljubljana on November 4^th, 1900, between members of a German gymnastics organization from Ljubljana and sports club from Graz. In that same year, a football section was established as part of the German sports club Laibacher Sportverein, but it was only active for a short time. In the following years, German and Slovene students eventually took the lead. Both had already gotten familiar with various ball games back in high school. From around 1906, a real little football euphoria began to develop. The youth was playing everywhere; teams were formed at high schools and informal student clubs outside them. In times of tense interethnic relations, the club Hermes, which had acquired a suitable pitch in Tivoli and invited student clubs from outside Ljubljana, took over the role of the representative of the Slovenian student football.

The process of forming a real Slovenian bourgeois sports club Ilirija began simultaneously in May 1911, laying the foundations for further development of football in Ljubljana. After only a year, Ilirija already strengthened its team with the top players from student clubs and invited many different clubs, especially Croatian and Czech, to friendly matches. The most famous guest was Slavia from Prague, one of the best clubs in Europe back then. In the war year of 1914, Ilirija moved to the former racetrack in Tivoli, where they also played qualifying matches for the city championship. It was the place for the first and reserve team of Ilirija, Slovan and Olimpija, while Vzajemnost had already been disbanded. The First World War interrupted further development.

Ljubljana derby between Ilirija and Primorje

As soon as the war ended, football was rapidly developing in the new Yugoslav state. In spring of 1919, Ilirija and Slovan recommenced their activities, and new clubs began to emerge, gradually becoming part of the Ljubljana Football Subassociation (Slov. Ljubljanska nogometna podzveza – LNP), founded in April 1920. This was dominated for many years by the circle around Ilirija. In May 1920, Ilirija opened its new pitch near the Šiška brewery and in the same year won the first LNP championship. For better revenue, strong foreign clubs were invited to friendly matches that were also attended by several thousands of spectators. A number of cup and youth competitions took place during this period as well.

After a few years, Ilirija finally got a serious domestic competitor – Primorje, a sports club representing emigrants from the Primorska region, which was at that point occupied by Italy. A real derby developed between the two clubs, backed by a large number of spectators. As the LNP champions, both clubs also had the opportunity to prove themselves in the national championship, which they had organized since 1923, but neither was overly successful. However, Ilirija reached the semi–finals of the National Cup in its inaugural season of 1930/31.

The duel for dominance on the pitch and in the Ljubljana Football Subassociation was leaving a financial mark on the clubs in the early 1930s. After several unsuccessful attempts, the two leading Ljubljana clubs merged on April 26^th, 1936. The goal was to create one strong club that could compete at state level. The unification of the football tradition of Ilirija and Primorje was formally carried out in a way that the former dissolved its football section, while the latter was transformed into the new Ljubljana Sports Club (Slov. Sportni klub Ljubljana). It took over Primorje's position in the championship and stadium, while most positions of team members and officials were taken by the team of Primorje. Nevertheless, in the end the project did not achieve the desired goals. The club remained too strong for local opponents, while it failed to achieve better results on the national level.

Other clubs in Ljubljana

Ljubljana had a bunch of clubs. Some were more successful, others existed only on paper or served as “satellite” clubs of Ilirija and Primorje, and some were so–called wild or unregistered clubs. Nonetheless, they all faced problems, especially financial ones, and therefore had large fluctuations in results. The southern part of the city was reigned by the Jadran (Trnovo) in the 1920s, which later developed a derby with Reka (Vič). At the same time, they were also competing against Svoboda, Krakovo and Vič. The eastern part of the city was also strongly represented in terms of numbers: Mars (Poljane), Slavija (Vodmat), Moste, Svoboda Moste, Grafika and the Catholic Mladika (Kodeljevo). The latter was led by the Salesians, as was Korotan at Rakovnik. Hermes from Spodnja Šiška, which joined forces with the Directorate of State Railways in 1925, may be pointed out as the third pillar of football in Ljubljana. This allowed Hermes to set up a third regular football pitch in 1931, which was upgraded to a modern stadium just before the war. Ljubljana basically suffered from a lack of suitable football pitches, and the void was filled by the pitches of Ilirija and Primorje for many years.

Football during the Second World War

In 1939, both politics and football were reorganized. In November, the Slovenian Football Association (Slov. Slovenska nogometna zveza – SNZ) was established in Ljubljana, which substituted the LNP. In autumn, it organized the Slovenian league, where club Ljubljana was declared champion. With the Italian occupation of Ljubljana in April 1941, football in the city did not disappear completely, but it faced many challenges. The first friendly was played in May, followed by the Slovenian Football Association Cup and the Ljubljana Province Championship, which was aborted. The new championship took place in the spring and summer of 1943, after wars and unstable weather conditions had paralyzed most of 1942. However, several tournaments and friendly matches were still played during that time. Club Ljubljana had always been at the top, while new clubs Žabjak and Iztok have entered the scene.

In September 1943, Italy capitulated and the city was occupied by the Germans. Players did not return to fields until 1944, when some high–profile tournaments were organized. By the end of the year, contacts between the clubs from Ljubljana and the Carinthian (Koroška) and Upper Carniola (Gorenjska) regions were renewed, which brought some well–attended matches. The last official match during the occupation took place on December 11^th, 1944, between Hermes and the Upper Carniola (Gorenjska) national team, followed by a standstill until the liberation on May 9^th, 1945. It was only eleven days later that the first friendly match in the free country was played between club Ljubljana and partisans’ 7^th corpus.