Agonopterix trimenella is a moth in the family Depressariidae.

It was described by Thomas de Grey, 6th Baron Walsingham, in 1881.

The forewings are pale ochreous, partly suffused with a pale brownish shade, especially on the lower half of the wing before the middle, at the extreme end of the cell, and immediately above the anal angle.

There is a large blackish patch, starting at the middle of the costa, continued more than half-way to the apex, extending nearly half across the wing, where it ends at its inner angle in a conspicuous black spot, preceded by some detached black scales.

Before this patch are three or four blackish spots on the costa, other smaller ones being distributed around the apical margin.