Eudonia synapta is a moth in the family Crambidae.

The forewings are white, sprinkled with ochreous brown and black.

The basal area is ochreous brown, suffused with black and cut by a narrow white transverse line midway between the base and the first line.

This first line is margined by black posteriorly, except in the middle.

The hindwings are grey, but the apex and hindmargin are darker.