| Gomphillus | Gomphillus calycioides |
| Gowardia | Gowardia nigricans |
| Graphina | Graphina anguina - see Graphis inustuloides |
| Graphina ruiziana - see Graphis ruiziana | |
| Graphis | Graphis alboscripta - see Fissurina alboscripta |
| Graphis elegans | |
| Graphis inustuloides | |
| Graphis pulverulenta | |
| Graphis ruiziana | |
| Graphis scripta | |
| Gyalecta | Gyalecta biformis |
| Gyalecta carneola - see Pachyphiale carneola | |
| Gyalecta carneolutea - see Cryptolechia carneolutea | |
| Gyalecta derivata | |
| Gyalecta jenensis - see Secoliga jenensis | |
| Gyalecta jenensis var. macrospora - see Secoliga macrospora | |
| Gyalecta truncigena | |
| Gyalecta ulmi - see Phialopsis ulmi | |
| Gyalidea | Gyalidea fritzei |
| Gyalidea hyalinescens var. hyalinescens | |
| Gyalidea hyalinescens var. pauciseptata | |
| Gyalidea roseola | |
| Gyalideopsis | Gyalideopsis muscicola |
| Gyalolechia | Gyalolechia bracteata |
| Gyalolechia flavovirescens | |
| Gyalolechia fulgens | |
| Gyrographa | Gyrographa gyrocarpa |
| Gyrographa saxigena |