Family name Iarlaith (Iarlaith 
) , in all the world, is an extremely rare surname. Much more frequently, Iarlaith is the forename as well as the last name.
| VARIANT | COUNTRY |
|---|---|
| Iarlaith | United Kingdom, Ireland, Myanmar, United States |
|
naomh iarlaith Irish priest and scholar from Connacht, IE (b. 445) |
|