Oberallgäu is a district in Bavaria, Germany. It is bounded by (from the north and clockwise) the districts of Unterallgäu and Ostallgäu, the Austrian states Tyrol and Vorarlberg, the district of Lindau, and the state of Baden-Württemberg (district Ravensburg). The city of Kempten is enclosed by, but not belonging to the district.
Human settlement dates back to the Bronze Age, when Celtic peoples inhabited the region. The Romans established a military camp which grew to become the city of Cambodunum, the present Kempten. It is consequently sometimes claimed that Kempten is the oldest town in Germany.
In medieval times Kempten was a free imperial city, and the surrounding lands became subordinate to the lords of Staufen and the counts of Rothenfels. Both ceased to exist in the beginning of the 19th century, when Napoleon handed these territories over to Bavaria.
The district of Oberallgäu was established in 1972 by merging the former districts of Sonthofen and Kempten.