The Landtag of Prussia was the representative assembly of the Kingdom of Prussia implemented in 1849, a bicameral legislature consisting of the upper House of Lords (Herrenhaus) and the lower House of Representatives (Abgeordnetenhaus). After World War I and the German Revolution of 1918–19 the Landtag diet continued as the parliament of the Free State of Prussia between 1921 and 1934, when it was abolished by the Nazi regime.

The Prussian House of Lords in Berlin was the upper house of the Landtag of Prussia, the parliament of Prussia from 1850 to 1918. Together with the lower house, the House of Representatives, it formed the Prussian bicameral legislature. The building is now used as the seat of the German Bundesrat.