The Rupes Altai quadrangle of the Moon is in the rugged, cratered terra of the southeastern earthside hemisphere. East-northeast of the quadrangle lies Mare Nectaris, approximately 350 km in diameter, and near the northeast corner is the crater Theophilus. Rupes Altai (the Altai scarp) divides the quadrangle into two markedly different morphologic provinces. To the west, complexly overlapping, fractured craters are extensively buried by distinctive noncrater units. The area east of the scarp, here referred as the bench and trough province, is part of the multi-ringed structure (Nectaris basin) whose deep central part is occupied by Mare Nectaris (Hartmann and Kuiper, 1962) and whose western limit is the scarp. This province is characterized by fewer craters and by benches and troughs which are only shallowly filled. Mare material of Mare Nectaris in contact with the bench and trough materials is locally exposed in the northeast corner of the quadrangle and more extensively just beyond the east border of the quadrangle. In general morphology, the Nectaris basin is similar to the Orientale basin (McCauly, 1968), but the Nectaris ring structures and other features are more subdued. Bright rays and satellite craters of the relatively young, probably impact craters Tycho and Theophilus cover much of the quadrangle.