Riiser-Larsen Sea is a marginal sea of the Southern Ocean. It is located between the Lazarev Sea to the west and the Cosmonauts Sea to the east, or between the 14°E and 30°E. Its northern border is defined to be the 65th parallel South. Depths exceed 3,000 meters in most of the sea. It is covered with drifting ice almost year-round. It stretches over an area of 1,138,000 km². . There are many icebergs.
To the south of Riiser-Larsen Sea lie Princess Astrid Coast and Princess Ragnhild Coast of Queen Maud Land. In the western part is the Lazarev Ice Shelf, and further east are Erskine Iceport and Godel Iceport, and the former Belgian Roi-Baudouin Station.