Football club Ilirija was founded on 9 June 1911[3] in a pub called Roža on Židovska cesta in Ljubljana.

In the first few years Ilirija had no competition in Slovenia and they mainly played friendly matches against Zagreb-based Croatian clubs such as HAŠK, Građanski and Concordia.

[4] An important turning point was a friendly with the Czech side Slavia Prague in Ljubljana played on 5 August 1913, which Ilirija lost 10–0.

[4] By the mid-1930s both Ilirija and Primorje encountered financial difficulties which led to their merger and the formation of SK Ljubljana football club in 1936.

In addition, Ilirija's Stanko Tavčar was the first Slovenian player who was capped for the Kingdom of Yugoslavia national football team in the period between the two world wars.

The team, composed of Jerebic, Rojina, Šmon, Erjavec, Kolenc, Dermastija, Godler, Ahlin, Filip, Jalšavec, Jesenšek, Daneu and Prelovšek, therefore contested for amateur championship of Yugoslavia that year, but lost against Vrbas in the final.

In the interwar period, Ilirija played its home matches on the field by Celovška Road, which was built in 1919 and was located between the State Station and the Union Brewery.