On the distant May 9, 1911, at the Roža tavern on Židovska Street in Ljubljana, the initiators and later founders of the football club Ilirija, considered the predecessor of Olimpija, gathered. Among those present were Dr. Ivan Lah, merchant Rohrmann, bank officials Dev and Est, as well as Kandare, Mencinger, Jurman, Berce, and Cerk. Albin Kandare was elected as the club’s first president.

In the early days, the footballers played on a field where the Union Brewery stands today, later moving to the Ilirija summer gymnasium. Their first match, against the Ljubljana student club Hermes, ended in a heavy defeat: 0–18. This loss quickly made the club’s leadership realize that strengthening the team would be essential to competing successfully with other clubs, particularly those from Croatia and Austria.

The solution came from the players of Hermes themselves. Ilirija began recruiting individual Hermes players, and soon the entire Hermes team was playing for Ilirija. The merging of the two clubs was completed in 1913. That same year, on August 5, Ilirija hosted the renowned Prague-based club Slavia. This was a significant moment, as it marked Ilirija’s first match against a professional team. Following the match, Slavia lent their coach, Jirkovský, to the Ljubljana club. He stayed in Ljubljana and introduced much-needed professionalism to the team.

By the start of World War I, Ljubljana was home to two football clubs: NK Ilirija and NK Slovan. However, during the war, football activities came to a complete halt.