| Conventional Long Name: | Ostmark |
| Common Name: | Austria |
| Subdivision: | Reichsgau |
| Nation: | Nazi Germany |
| P1: | Federal State of Austria |
| Flag P1: | Flag of Austria.svg |
| S1: | Nazi Germany |
| Flag S1: | Flag of German Reich (1935–1945).svg |
| Flag: | List of German flags |
| Capital: | Vienna |
| Year Start: | 1938 |
| Year End: | 1939 |
| Title Leader: | Reichsstatthalter |
| Leader1: | Arthur Seyss-Inquart |
| Year Leader1: | 1938–1939 |
Ostmark (in German pronounced as /ˈɔstmaʁk/, "Eastern March") was a name that referred historically to the Margraviate of Austria, a medieval frontier march. It was also used in Nazi propaganda from 1938 to 1942 to refer to the formerly independent Federal State of Austria after the Anschluss with Nazi Germany. From the Anschluss until 1939, the official name used was Land Österreich ("State of Austria").[1]
Once Adolf Hitler completed the union between Austria and Germany (Anschluss), the Nazi government had the incorporated territory renamed. The name Austria (Österreich in German, meaning "Eastern Realm") was at first replaced by "Ostmark", referring to the 10th century Marcha orientalis. The change was meant to refer to Austria as the new "eastern march" of the Reich.
In August 1938, the Donau-Zeitung proudly referred to Passau as "the cradle of the new Ostmark".[2]
According to the Ostmarkgesetz with effect from 1 May 1939, the former States of Austria were reorganized into seven of the German Reich, each under the rule of a government official holding the dual offices of Reichsstatthalter (governor) and Gauleiter (Nazi Party leader):[3]
A Reichsgau was a new, simple administrative sub-division institution which replaced the federal states in the otherwise completely centralized Third Reich.[4] From April 8, 1942, as the term "Ostmark" was still too reminiscent of the old, independent state of Austria, the chosen official name for the seven entities was Alpen- und Donau-Reichsgaue ("Danubian and Alpine Reichsgaue"). In the course of the Allied occupation after World War II, the Austrian state was restored in its pre-1938 borders according to the 1943 Moscow Declaration.