Erynnis horatius, commonly known as Horace's duskywing, is a species of butterfly in the family Hesperiidae.

It is found in the United States from Massachusetts to Florida, and west to eastern South Dakota, the Gulf Coast, south-eastern Utah, Colorado, north-eastern Arizona, and New Mexico.

Upperside of male forewing is dark brown with little contrast and no white overscaling.

Upperside of female forewing is light brown with a contrasting pattern and large transparent spots.

Adults consume nectar from flowers up to about 4.5 feet (1.4 m) above ground level, including those of dogbane, buttonbush, sneezeweed, goldenrod, peppermint, boneset, and winter cress.