Callophrys hesseli, or Hessel's hairstreak, is a butterfly of the family Lycaenidae. It ranges from southern Maine south along the Atlantic coastal plain to the Florida Panhandle on the Gulf Coast. The species was first described (as Mitoura hesseli) by George W. Rawson and J. Benjamin Ziegler in 1950, in honor of the lepidopterist Sidney Adolphus Hessel. It is listed as endangered in Connecticut by state authorities due factors such as logging and insecticide.

These butterflies live in wetlands, as that is where the Atlantic white-cedar (Chamaecyparis thyoides) thrives. The whole lifecycle of these butterflies depends on this tree. The caterpillars feed off the foliage of the tree, then the adult butterflies will mate and lay their eggs on the tree. Adults consume nectar from flowers including swamp milkweed, shadbush, sand myrtle, sweet pepperbush, highbush blueberry, buttonbush, and dogbane.

The Hessel's hairstreak wings have their unique identifier of olive green and rusty brown colors. It has adapted to camouflage with the Atlantic white-cedar in both its caterpillar and butterfly form.

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