Reichstag (English: Diet of the Realm or Imperial Diet) is a German word generally meaning parliament. Historic legislative bodies in German-speaking countries have been referred to as Deutscher Reichstag, including:
- Imperial Diet (Holy Roman Empire), called the Reichstag in the HRE from about 15th century, earlier known as the Hoftag (777–1806)
- Imperial Diet (Austria), first elected parliament of the Austrian Empire as part of the German Confederation (1848–1849), known as the Reichstag
- Reichstag (North German Confederation), parliament of the North German Confederation (1867–1870)
- Reichstag (German Empire), parliament of the German Empire (1871–1918)
- Reichstag (Weimar Republic), parliament of the Weimar Republic (1919–1933)
- Reichstag (National Socialist Germany), parliament of the Third Reich (1933–1945)
Scandinavian parliamentary bodies which bear or bore the name Riksdag are also called Reichstag when referred to in the German language; these words have the same origin. Also, the Diet of the Empire of Japan was first established as the "Imperial Diet" in 1890 under the Meiji Constitution.