| Name | Gender | Pronounced | Usage | Popularity |
|---|---|---|---|---|
| Idwal | - | Welsh | ||
| Iefan | - | Welsh | ||
| Iestyn | - | Welsh | ||
| Ieuan | - | Welsh | ||
| Ifan | - | Welsh | ||
| Ilar | - | Welsh | ||
| Illtyd | - | Welsh | ||
| Ioan | - | Romanian, Welsh, Bulgarian | ||
| Iolo | - | Welsh | ||
| Iolyn | - | Welsh | ||
| Iorwerth | - | Welsh | ||
| Islwyn | - | Welsh | ||
| Ithel | - | Welsh | ||
| Ivor | IE-vawr (English), EE-vawr (English) | Irish, Scottish, Welsh, English (British) | ||
| Iwan | EE-wan (Welsh), EE-vahn (Polish) | Welsh, Polish |