- TWM O'R NANT - see EDWARDS, THOMAS
- TWM PEDROG - see WILLIAMS, THOMAS
- TWM SBAEN - see JONES, THOMAS
- TWM SHÔN CATI - see JONES, THOMAS
- TWM SIÔN CATI - see JONES, THOMAS
- TYDECHO (fl. 6th century), Celtic saint
- TYDFYLYN - see WILLIAMS, DANIEL THOMAS
- TYSILIO (fl. 7th century), Celtic saint