The Isarkreis (German: Isar District) was one of the 15 administrative districts (German: Bezirke or Regierungsbezirke) of the Kingdom of Bavaria between 1806 and 1837.

It was the predecessor of the Regierungsbezirk Oberbayern (Administrative District of Upper Bavaria).

In the years between 1806 and 1808 the Kingdom of Bavaria was divided into 15 districts.

In 1817, there was another reshuffle; some areas were added and other ones given to the Upper Danube District (Oberdonaukreis).

In another territorial reorganization initiated by King Ludwig I on 29 November 1837, the Isarkreis was renamed Upper Bavaria (Oberbayern).