A putative Potexvirus was detected from bottle gourd (Lagenaria siceraria) showing mosaic and mottle symptoms in Myanmar in 2007. The virus was designated Lagenaria mild mosaic virus (LaMMoV) and was further characterized. In artificial inoculation tests, infectivity of LaMMoV was limited to two families: Chenopodiaceae and Cucurbitaceae. The host range of LaMMoV differs from those of the two cucurbit-infecting potexviruses, Alternanthera mosaic virus (AltMV) and Papaya mosaic virus (PapMV). Sequence analyses of LaMMoV showed that the C-terminal 3,859 nucleotides, excluding the poly-A tail, includes the C-terminal region of an RNA-dependent RNA polymerase (RdRp), a triple gene block (TGB), a coat protein (CP), and a 3' untranslated region (UTR), all of which are typical of potexviruses. Although LaMMoV is related closely to AltMV and PapMV, its nucleotide sequences differ from those of other previously reported potexviruses. Therefore, we report LaMMoV as a new species of the genus Potexvirus that occurs in the cucurbit bottle gourd.