| Ramularia | Ramularia centranthi |
| Ramularia digitalis-ambiguae | |
| Ramularia endophylla | |
| Ramularia pratensis | |
| Ramularia unterseheri | |
| Rebentischia | Rebentischia unicaudata |
| Rhagadostoma | Rhagadostoma verrucariarum |
| Rhamphoria | Rhamphoria sp. P1035 |
| Rhizodiscina | Rhizodiscina lignyota |
| Rhizosphaera | Rhizosphaera kalkhoffii |
| Rhopographus | Rhopographus filicinus |
| Rhymbocarpus | Rhymbocarpus neglectus |
| Rhytisma | Rhytisma acerinum |
| Rhytisma maximum | |
| Rhytisma salicinum - see Xyloma salicinum | |
| Rosellinia | Rosellinia britannica |
| Rosellinia corticium | |
| Rosellinia franciscae | |
| Roselliniella | Roselliniella cladoniae |
| Roselliniella stereocaulorum | |
| Roselliniopsis | Roselliniopsis tartaricola |
| Roseodiscus | Roseodiscus subcarneus |