| Name | Gender | Pronounced | Usage | Popularity |
|---|---|---|---|---|
| TiarnÁN | - | Irish | ||
| Tiarnach | - | Irish | ||
| Tiernan | - | Irish | ||
| Tierney | TEER-nee | Irish, English (Rare) | ||
| TigernÁN | - | Irish | ||
| Tigernach | - | Irish | ||
| Tighe | - | Irish | ||
| TighearnÁN | TEER-nawn | Irish | ||
| Tighearnach | TEER-nakh | Irish | ||
| Toal | - | Irish | ||
| ToirÉAsa | - | Irish | ||
| Toirdhealbhach | - | Irish | ||
| TomÁS | to-MAHS (Spanish), too-MASH (Portuguese) | Spanish, Portuguese, Irish | ||
| Torin | - | Irish | ||
| Treasa | TRA-sa | Irish |