Lasionycta subalpina is a moth of the family Noctuidae. It is found from southern Idaho and the Beartooth Plateau on the Montana-Wyoming border to Colorado and central Utah as well as in the Sierra Nevada of California.
The habitat is subalpine forests and mid-elevation pine forests.
The wingspan is 29–33 mm for males and 30–35 mm for females. Adults are on wing from mid-July through August.