Basdahl is a municipality in the district of Rotenburg, in Lower Saxony, Germany.

Its parliament, the Bremian Estates (German: Stiftsstände), convened in diets (Tohopesaten or Landtage) usually in Basdahl, with Bremervörde serving as capital with the prince-archiepiscopal residence and seat of government (as of 1219).

In 1648 the Prince-Archbishopric was transformed into the Duchy of Bremen, which was first ruled in personal union by the Swedish Crown - interrupted by a Danish occupation (1712–1715) - and from 1715 on by the Hanoverian Crown.

In 1813 the Duchy was restored to the Electorate of Hanover, which - after its upgrade to the Kingdom of Hanover in 1814 - incorporated the Duchy in a real union and the Ducal territory, including Basdahl, became part of the new Stade Region, established in 1823.

Basdahl's historical role in the prince-archbishopric is commemorated in its coat-of-arms showing on the left side the crisscrossed keys, the coat-of-arms of the prince-archbishopric.