| Newcastle | |
| Native Name: | An Caisleán Nua (Irish) |
| Settlement Type: | Barony |
| Subdivision Type: | Sovereign state |
| Subdivision Name: | Ireland |
| Subdivision Type1: | County |
| Subdivision Name1: | Wicklow |
| Area Total Km2: | 210.19 |
| Area Total Sq Mi: | 81.15 |
Newcastle is a barony in County Wicklow, Ireland.
Newcastle barony derives its name from the village of Newcastle.
Newcastle barony is located in eastern County Wicklow, opening onto the Irish Sea.
The Uí Theig (O'Tighe), cousins to the Uí Máil, are noted early here, as well as the Uí Braen Deilgni, a branch of the Uí Garrchon. This was part of O'Byrne (Ó Broin) country after the 12th century, referred to in Gaelic as Crioch Branach.[1]
Below is a list of settlements in Newcastle barony: