Dirina fallax is a species of saxicolous (rock-dwelling), crustose lichen in the family Roccellaceae.

[1] The lichen was first described scientifically by Giuseppe De Notaris in 1846, from specimens collected in Sardinia, Italy.

[3] The lichen has a creamy greyish-brown, crustose thallus with a somewhat roughened surface (0.1–1.5 mm thick), and a white, chalk-like medulla.

If apothecia are present, they have a circular outline and a diameter of 0.1–2.0 mm; the apothecial disc is white-grey, pruinose, and encircled by a thalline margin.

Dirina fallax contains the lichen products erythrin and lecanoric acid, as well as two unidentified substances.