Ostrubel (German and Polish: ; Latvian and Lithuanian: ; ) is the name given to a currency denominated in copecks and rubels, which was issued by Germany in 1916 for use in the eastern areas under German occupation ( and the Government General of Warsaw). It was initially equal to the Imperial rouble. The reason for the issue was a shortage of currency. The banknotes were produced by the Darlehnskasse, a unit of the Ostbank für Handel und Gewerbe in (now ) on 17 April 1916.
From 4 April 1916, the circulated alongside the in the area, with = 1 . In the Government General of Warsaw the was replaced by the Polish on 14 April 1917.
The banknote denominations available were:
The front sides of the banknotes carry a warning in German against forging banknotes. On the reverse sides is the same warning in Latvian (with old style orthography), Lithuanian and Polish.
There were also 1 copeck, 2 copeck and 3 copeck coins, made out of iron.
The circulated in Lithuania together with the Ostmark until 1 October 1922, when it was replaced by the .
It was also still in use in a part of the Second Polish Republic during the first months of independence, until 29 April 1920.