Here we report a new large-bodied sivaladapid based on an isolated M3 from Pondaung, described as Guangxilemur rarissimus sp. nov. The tooth exhibits diagnostic features of Guangxilemur, including a subrectangular outline, a deep trigon basin, an incipient mesostyle, a well-developed buccal cingulum, and pronounced enamel wrinkling. Its dimensions indicate a body mass of approximately 4.1–4.8 kg, substantially larger than previously known Pondaung strepsirrhines and closely matching estimates for the controversial partial postcranial skeleton NMMP 20, previously attributed to the amphipithecine Pondaungia. Because NMMP 20 displays clear strepsirrhine affinities and corresponds in size to G. rarissimus, we reassign this specimen to the new taxon.