Coprosylia bisetosa new genus and new species (Diptera: Sphaeroceridae: Limosininae) is described on the basis of four males and one female found riding on the abdominal sternites of a dung-rolling scarab beetle (Paragymnopleurus maurus [Sharp]) in Sarawak, Malaysia. This is the first record of phoretic Diptera associated with coprophagous beetles in Southeast Asia. The new species is presumed to be kleptoparasitic in dung balls sequestered by host beetles.