| Takakiopsida | see Bryophyta |
| Taphrinomycotina | see Ascomycota |
| Tardigrada | EUKARYA>UNIKONTA>OPISTHOKONTA>ANIMALIA>BILATERIA>PROTOSTOMATA>ECDYSOZOA>PANARTHROPODA>TARDIGRADA |
| Tetraphidiopsida | see Bryophyta |
| Thelodontomorphi | EUKARYA>UNIKONTA>OPISTHOKONTA>ANIMALIA>BILATERIA>DEUTEROSTOMATA>VERTEBRATA>THELODONTOMORPHI |
| Thermobacteria | ARCHAEA>EURYARCHAEOTA>THERMOBACTERIA |
| Thermoplasmobacteria | ARCHAEA>EURYARCHAEOTA>THERMOPLASMOBACTERIA |
| Thermotogabacteria | EUBACTERIA>PROTEOBACTERIAE>THERMOTOGAE>THERMOTOGOBACTERIA |
| Trebouxiophyceae | see Chlorophyta |
| Trilobitomorpha | EUKARYA>UNIKONTA>OPISTHOKONTA>ANIMALIA>BILATERIA>PROTOSTOMATA>ECDYSOZOA>PANARTHROPODA>ARTHROPODA>TRILOBITOMORPHA |
| Trimerophytophyta | EUKARYA>ARCHAEPLASTIDA>VIRIDIPLANTAE>STREPTOBIONTA>EMBRYOPHYTA>TRACHEOPHYTA>TRIMEROPHYTOPHYTA |
| Trochozoa | see Spiralia |
| Tunicata | EUKARYA>UNIKONTA>OPISTHOKONTA>ANIMALIA>BILATERIA>DEUTEROSTOMATA>TUNICATA |
