Erynnis icelus, also known as the dreamy duskywing or aspen dusky wing, is a species of butterfly in the family Hesperiidae.

There is one generation with adults on wing from April to early July.

[citation needed] The larvae are pale green with multiple white dots.

[2] The larvae feed on Salix, Populus and sometimes Betula species.

Adults feed on nectar from flowers of blueberry, wild strawberry, blackberry, Labrador tea, dogbane, New Jersey tea, winter cress, purple vetch and lupine.