The Loibl Pass or Ljubelj Pass is a high mountain pass in the Karavanke chain of the Southern Limestone Alps, linking Austria with Slovenia. The century-old pass near the Stol summit is the shortest connection between the Carinthian town of Ferlach and Tržič in Upper Carniola.
Different trails were used since ancient times, connecting Virunum in the Roman province of Noricum with Emona (at present-day Ljubljana). The strategically importance of the Loibl increased again after the establishment of the Imperial March of Carniola in the 11th century, the ruling Patriarchs of Aquileia entrusted the maintenance to the monks of Viktring Abbey, who rivaled with claims raised by the local Lords of Hollenburg (Humberk) Castle.
The first army vehicles passed the very tight tunnel on 4 December 1944. Military traffic, Wehrmacht soldiers retreating from the Yugoslav Front and refugees used the tunnel until it was closed in 1947. Then a border crossing between Austria and the Federal People's Republic of Yugoslavia, it was reopened in 1950 and expanded to two lanes in 1966, while the old road over the mountain pass itself has been closed for traffic since 1967.
The importance of the Loibl Pass has diminuished since 1991, when the 7,864 m (25,801 ft) long Karawanken Motorway Tunnel, which connects the Austrian Karawanken Autobahn (A 11) from Villach with the Slovenian A2 motorway to Ljubljana. Border controls have been abolished with Slovenia joining the Schengen Area effective from 21 December 2007.