| Saccharomycotina | see Ascomycota |
| Saprospirae | EUBACTERIA>PROTEOBACTERIAE>SAPROSPIRAE |
| Saprospirobacteria | EUBACTERIA>PROTEOBACTERIAE>SAPROSPIRAE>SAPROSPIROBACTERIA |
| Scalidophora | see Ecdysozoa |
| Selaginellopsida | see Lycopodophyta |
| Silicoflagellata | EUKARYA>CHROMALVEOLATA>HETEROKONTAE>SILICOFLAGELLATA |
| Sphagnopsida | see Bryophyta |
| Spiralia | EUKARYA>UNIKONTA>OPISTHOKONTA>ANIMALIA>METAZOA>BILATERIA>PROTOSTOMATA>SPIRALIA |
| Spirochaetae | EUBACTERIA>PROTEOBACTERIAE>SPIROCHAETAE |
| Spirochaetobacteria | EUBACTERIA>PROTEOBACTERIAE>SPIROCHAETAE>SPIROCHAETOBACTERIA |
| Stegocephali | EUKARYA>UNIKONTA>OPISTHOKONTA>ANIMALIA>BILATERIA>DEUTEROSTOMATA>VERTEBRATA>GNATHOSTOMATA>TETRAPODA>STEGOCEPHALI |
| Streptobionta | see Green Algae |
| Syndermata | EUKARYA>UNIKONTA>OPISTHOKONTA>ANIMALIA>BILATERIA>PROTOSTOMATA>SPIRALIA>PLATYZOA>GNATHIFERA>SYNDERMATA |