For information on the military unit see Grossdeutschland Division
Grossdeutschland (from the German Großdeutschland, literally Greater Germany) is a term that has been used in two separate contexts over history.
German Unification
Grossdeutschland was a 19th century political idea postulating the (never realized) idea of a unified Germany, led by Habsburg Austria and with Vienna as its capital, as opposed to the Prussian-led alternative, known as Kleindeutschland (Small Germany). With the foundation of the German Empire in 1871, which did not include Austria, the Kleindeutschland solution was put into practice.
In a reference to the earlier concept of Grossdeutschland, after the Anschluss (annexation) of Austria to the Deutsches Reich (German Empire) in 1938, the state was informally renamed to Grossdeutsches Reich.