Leimonis erratica is a species of crustose lichen in the family Pilocarpaceae. A widely distributed species that grows on siliceous rock, it is found in Asia, Australia, North America, and Réunion.
The lichen was originally described in 1861 by German lichenologist Gustav Wilhelm Körber as a member of genus Lecidea. In 2009, Richard Harris and James Lendemer transferred it to the new genus Leimonis, in which it is the type species.