Amastra undata is a species of air-breathing land snail, a terrestrial pulmonate gastropod mollusc in the family Amastridae.

It has a dark reddish-brown color, with broad, irregular light yellow stripes on the last two whorls.

These stripes form a zigzag pattern below the periphery, blending together above it, and are preceded by scattered whitish spots and dashes on one or two earlier whorls.

The aperture is subvertical, with a flesh-colored interior and a white callous rim within the lip.

[2] This very rare species is endemic to Hawaii, occurring on Oahu Island.