Castlebar is the county town of, and at the centre of, County Mayo in Ireland. It is Mayo's largest town by population. The town's population exploded in the late 1990s, increasing by one-third in just six years, though this massive growth has slowed down greatly in recent years. A campus of Galway-Mayo Institute of Technology and the Country Life section of the National Museum of Ireland are two important local amenities.
The town is connected by railway to Dublin and the neighbouring Mayo towns of Westport and Ballina. The town has several small satellite villages around it, such as Breaffy and Parke. The main route by road is the N5. Its economy is primarily service-based. The modern town grew up as a settlement around the de Barry castle, which was built by a Norman adventurer in 1235 and was later the site of an English garrison.The castle was located at the end of Castle Street, where the town river is thought to have originally flowed. A military barracks operates in the town to this day; armed conflict has been the centrepiece of the town's historical heritage.