Satyrium favonius, the oak hairstreak or southern hairstreak, is a butterfly of the family Lycaenidae. It is found in the United States from southern New England and the Atlantic Coast south to peninsular Florida and west to central Illinois, south-eastern Colorado and the Gulf Coast.

The wingspan is 22–38 mm.

The larvae feed on the leaves, buds and male catkins of Quercus species. The species overwinters as an egg.

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