| # | Name | Origin | Meaning | Gender | |
|---|---|---|---|---|---|
| 641 | Trevyn | Welsh | Fair town. Abbreviation of Trevelyan. | M | |
| 642 | Tringad | Welsh | Legendary son of Neued. | M | |
| 643 | Tristan | Welsh | Noisy. | M | |
| 644 | Tristram | Welsh | Sorrowful. | M | |
| 645 | Tristyn | Welsh | Tumult; outcry. From the Celtic name Tristan. | M | |
| 646 | Trynt | Welsh | Dwells near the rapid stream. | M | |
| 647 | Trystan | Welsh | Tumult; outcry. From the Celtic name Tristan. | M | |
| 648 | Tudor | Welsh | God's gift. | M | |
| 649 | Twm | Welsh | Welsh form of Tom 'gift from God'. | M | |
| 650 | Twrgadarn | Welsh | Tower of stlength. | M | |
| 651 | Tywysog | Welsh | Prince. | M | |
| 652 | Uchdryd | Welsh | Legendary son of Erim. | M | |
| 653 | Vaddon | Welsh | From Bath. | M | |
| 654 | Vaughan | Welsh | Little. | M | |
| 655 | Vaughn | Welsh | Variant of Vaughan: Little. | M | |
| 656 | Vonn | Welsh | Little. | M | |
| 657 | Vontell | Welsh | Little. | M | |
| 658 | Vorath | Welsh | Variant of Iorwerth: Worthy lord. Derived from 'ior' and 'gwerth'. Legendary son of Maredudd. | M | |
| 659 | Vychan | Welsh | Small. | M | |
| 660 | Wadu | Welsh | Legendary son of Seithved. | M | |