Elachista jupiter is a moth in the Elachistidae family. It was described by Sugisima in 2005. It is found in Japan (Hokkaidô). The length of the forewings is 3.3–3.9 mm for males and 3.3–3.5 mm for females. Adults are very similar to Elachista hiranoi, but can be distinguished by differences in coloration of the forewings. The markings are comparatively blurred and the fascia on is always interrupted around the fold. Adults have been recorded on wing from late May to early June, probably in one generation per year.