Mahoonagh or Castlemahon (Irish: Caisleán Maí Tamhnach) is a village and civil parish in County Limerick, Ireland. The village lies four kilometres south east of the town of Newcastle West.

There are two villages within the civil parish of Mahoonagh, namely Mahoonagh and Feohanagh (Feothanach) villages. Mahoonagh village is the official name and it is known locally as Castlemahon (Caisleán Uí Mhathúna) village.

There is one main street in Castlemahon and one main housing estate known as Churchview. There is a parish hall, a primary National School, a Roman Catholic church, two shops, one pub, one car garage and a plant hire company within the village.

From Newcastle West proceed out the 'Bruff line' road (towards Kilmallock) and after 1.5 miles (2.4 km) take the first right at the cross roads towards Kilmeedy. Mahoonagh/Castlemahon village is situated on the east bank of the River Deel.

Feohanagh village is situated approximately eight kilometres further away, on the R522 on the road between Newcastle West and Dromcollogher.

The Killarney/Tralee bus route passes through Newcastle West. The county's regional/national bus hub is located in Limerick City's Colbert Station train station. The bus hub has connections to various cities and towns throughout Ireland.

The nearest passenger rail is Charleville, County Cork. This lies on the Cork-Dublin line. The Limerick-Dublin line via Limerick Junction County Tipperary is also accessible.

No commercial airports are situated in County Limerick and the parish's needs are serviced from Shannon Airport, N19 road in County Clare, Kerry Airport Farranfore, N23 road County Kerry and Cork Airport, N27 road County Cork, all are within an hour's drive.