Earthworm specimens collected from the Nam Xam National Protected Area, Laos represent a new species of Megascolecidae: Amynthas hauyhowensis sp. nov. Amynthas hauyhowensis sp. nov. is in the hexathecus species group in Sims and Easton (1972), defined by having five pairs of spermathecae in 4/5-8/9. The species has secondary male pores equatorial in XVIII at the 11th setal lines, paired invaginated genital papillae postsetal on XVII anterior to male pores, and manicate intestinal caeca. A description of the new species is provided, including illustrations of the ventral view, intestinal caeca, prostate gland and representative spermathecae.