Syngrapha diasema is a species of moth in the family Noctuidae that was first described by Jean Baptiste Boisduval in 1829.

It is found from northern Fennoscandia to Siberia, across the Arctic and subarctic.

In North America, it has been reported across the Arctic and subarctic from Labrador to central Alaska.

Adults are on wing in July depending on the location.

The larvae feed on Betula species (including Betula nana) and Vaccinium and Populus species, as well as Trollius europaeus.