Margarethe Arndt-Ober (b. Berlin, April 15, 1885–d. Bad Sachs, March 17, 1971) was a German opera singer who had an active international career during the first half of the twentieth century. A highly skilled contralto, Ober enjoyed a particularly long and fruitful association with the Berlin State Opera from 1907 to 1944. She also was notably a principal singer at the Metropolitan Opera in New York City between 1913 and 1917.