Apodemus nigrus is a field mouse described in 2019 from high mountains in southeastern China. The study compared Chinese specimens using both genetic and morphological data and distinguished the species from close relatives.
The upper coat is black with fine brown speckling. The underside is grayish white and sharply contrasts with the back; the ears and limbs also show dark-and-pale contrast. The blackish-brown tail is slightly longer than the head and body.
Specimens were collected at about 1,984–2,130 m on Fanjing and Jinfo mountains. Alpine scrub, rhododendron, and bamboo are among the recorded vegetation at the sites; the paper discusses these mountains as refuges for temperate species.
An extinction-risk assessment has not been added yet.