Amphidromus niasensis is a species of air-breathing tree snail, an arboreal gastropod mollusk in the family Camaenidae.
Amphidromus cognatus is large, with a shell length ranging from and a diameter of .
(Original description) The sinistral shell is moderately thin and finely obliquely striated. The protoconch is semitransparent and waxy. The teleoconch has a light reddish base ornamented by moderately broad oblique stripes, bisected medially by a narrow spiral band of a paler hue. The base of the body whorl exhibits a moderately broad dark brown band just below the periphery and a narrower dark brown band further ventrally, separated by a yellow band. The umbilical region is reddish. The shell contains six convex whorls, increasing rather slowly. The aperture displays external markings internally. The peristome is slightly expanded and is flesh-colored. The columella is vertical, flesh-colored, rounded and slightly expanded at its insertion.
Amphidromus niasensis was found on Nias Island, off the werst coast of Sumatra.