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

The last 2–3 whorls are coated with a thin, dark brown cuticle, which is often shed in angular fragments or patches and is typically absent near the aperture.

The spire is slightly convexly conic and tapers to an acute apex, comprising 5½–5¾ nearly flat whorls.

The aperture is ovate and slightly oblique, lined with a distinct internal rib within the peristome.

The columella is short and moderately expanded, bearing a pronounced, spiral lamella.