Amastra is a genus of small air-breathing land snails, terrestrial pulmonate gastropod mollusks in the family Amastridae.

Like many Hawaiian land snails, species in this genus have adapted to a specific ecological niche and have evolved in relative isolation. They used to thrive in wet or moderately wet forested areas.

Unfortunately, many of the species in this genus have become extinct in recent times or have become critically endangered through habitat loss or, in most cases, predation by Euglandina rosea. This loss is often highlighted as part of the broader biodiversity crisis faced by the Hawaiian Islands.

Some individuals of remaining extant Amastra species were collected for captive breeding programs at the Bishop Museum and Snail Extinction Prevention Program. Reintroductions of some species are currently underway.

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