The 2008–09 Slovenian Cup was the 18th season of Slovenia's football knockout competition. It started on 2 August 2008 with the First Round games and ended on 30 May 2009 with the Final. The defending champions were Interblock.
In this round entered 19 teams from Slovenian second and third division. Since Izola withdrew from the competition before the beginning, Adria received a bye to the Second Round. The matches were played on 2 and 19 August 2008.
In this round entered winners from the previous round as well as all teams from the Slovenian PrvaLiga. Livar also entered in the Third Round. They got relegated to the second division at the end of the last year's PrvaLiga. The matches were played on 16 and 17 September 2008.