Reimnitzia is a fungal genus in the family Graphidaceae. This is a monotypic genus, containing the single lichen species Reimnitzia santensis. Both the genus and species were described as new to science in 2001 by German lichenologist Klaus Kalb. The genus name honours Michael and Christine Reimnitz, friends of the author who assisted him with his lichen collections. The type species was originally named Theletrema santensis by American Edward Tuckerman, from specimens collected by Henry William Ravenel in South Carolina. The main characteristic of the lichen is the distinct formed by the densely interwoven upper parts of the . Reimnitzia was originally classified in the Thelotremataceae, but that family has since been folded into the Graphidaceae.
Reimnitzia santensis has also been recorded in Ecuador, and China.