() is the name given to a currency denominated in which was issued by Germany in 1918 for use in a part of the eastern areas under German control at that time, the area. The currency consisted of paper money issued on 4 April 1918 by the Darlehnskasse Ost in (Kaunas) and was equal to the German. The circulated alongside the Imperial rouble and the , with two equal to one .
The denominations available were:
The reverse sides of the carry a warning against forging banknotes in German, Latvian and Lithuanian.
The Ostmark and Ostrubel continued to circulate in Lithuania from the end of World War I until 1 October 1922, when they were replaced by the . The names and were used for and , for example, on postage stamps. The reason for the replacement was the link to the , which already suffered from inflation (and would spiral into hyperinflation in 1923). The was pegged to the U.S. dollar.