Xenonectriella nephromatis is a species of lichenicolous fungus in the family Nectriaceae.

The type specimen was discovered in the Hoonah–Angoon Census Area in Glacier Bay National Park, where it was growing on a Nephroma lichen.

[1] The fungus has perithecioid ascocarps, meaning that they are spherical or flask-shaped with a central pore (ostiole) through which spores are discharged.

These dark red ascocarps, which are immersed in the thallus of the host lichen, are up to 0.6 mm in diameter.

Ascospores are more or less broadly ellipsoid, with some variation in shape, and measure 12–16 by 5–8 μm.