Diepholz (German pronunciation: [ˈdiːphɔlts]) is a district in Lower Saxony, Germany.

It is bounded by (from the northeast and clockwise) the districts of Verden, Nienburg, Minden-Lübbecke (in North Rhine-Westphalia), Osnabrück, Vechta and Oldenburg, and by the cities of Delmenhorst and Bremen.

At the beginning of the 16th century there was great pressure from the powerful duchy of Brunswick-Lüneburg, which tried to annex the smaller states.

By forming an alliance with the neighbouring County of Hoya and asking for help from the emperor himself the state of Diepholz managed to survive some more decades.

The district extends from the southern outskirts of Bremen to the border of North Rhine-Westphalia.