Bryolymnia semifascia, the half-banded bryolymnia, is a moth of the family Noctuidae.

The species was first described by John Bernhardt Smith in 1900.

It is found in the US from northern Colorado and southern Utah southward to south-eastern Arizona and south-central New Mexico.

Adults have been collected from mid-June to mid-September in conifer forests.

This Hadeninae-related article is a stub.