Tactusa brevis is a moth of the family Erebidae first described by Michael Fibiger in 2011.

The head, patagia and base of the costa are black and the ground colour of the forewings is brown, with a dark brown costal-medial patch, and with a dark brown subterminal and terminal area, including fringes.

The reniform stigma is beige yellow, outlined by black.

The biotope consists of a moist, mainly broad-leaf forest, with bushes and herbaceous plants, close to a river.

The Mojiang collecting site is a large ravine with a brook.