Curculio sayi, the small or lesser chestnut weevil, is a species of true weevil in the family of beetles known as Curculionidae.

The lesser chestnut weevil is found in North America. The distribution of this species extends from Canada and Massachusetts to North Carolina, Tennessee, and Ohio, and probably farther westward. This weevil is highly host-specific. It has only been observed to feed and oviposit on the genus Castanea (chestnut and chinquapin).

Before the arrival of the chestnut blight, small chestnut weevils and the greater Curculio caryatrypes were prominent pests of the American chestnut crop. Reports from the early 1900s mentioned that large losses in American chestnut production occurred due to infestation by Curculio larvae. American chestnut crop infestation rates between 50% and 75% were considered normal. With the spread of the chestnut blight in American chestnut trees, the strictly host specific Curculio caryatrypes may have become extinct. Curculio sayi is less host specific and reproduces in the chestnuts of other species of Castanea.

If left unchecked, weevil populations in an orchard can develop rapidly, reaching high levels of infestation in as little as two years. Infested nuts are less likely to germinate, if at all and nut damage affects chestnut seedling growth. The rate of nuts weevil infestation may vary between years, locations, cultivars, and even individual trees, burrs and nuts.

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