The Schirmacher Oasis (or Schirmacher Lake Plateau) is a 25 km long and up to 3 km wide ice-free plateau with more than 100 freshwater lakes. It is situated in the Schirmacher Hills on the Princess Astrid Coast in Queen Maud Land in East Antarctica, and is on average 100 metres above sea level. With an area of 34 km², the Schirmacher Oasis ranks among the smallest Antarctic oases and is a typical polar desert.
The oasis is located between the edge of the Antarctic Ice Sheet and the Novolazarevskaya Nivl Ice Shelf. The approximately 100 m high plateau of the Schirmacher Oasis is a barrier to the northwards running ice stream. On the northern edge of the oasis are so-called epishelf lakes, bays separated from the ocean, which are connected with the ocean underneath the surface of the ice. Thus, tidal effects can be observed in the lakes. The epishelf lakes can contain either mere freshwater or saltwater which is overlaid by freshwater. The Antarctic Ice Sheet, southwards of the Schirmacher Oasis, reaches heights of 1500 m. The nunataks Skaly Instituta Geologii Arktiki (Skaly IGA) and Basisny-Kit protrude from the ice sheet. Between the offshore ice sheet and the Wegener Ice Sheet Plateau are the Wohlthat Mountains.
The highest part of the Schirmacher Oasis is Mount Rebristaya with a height of 228 m. With its 34.5 m Lake Glubokoye is the deepest inland lake of the oasis. Spatially the largest lake within the oasis is Lake Sub with 0.5 km².