Chip maker American Power Conversion is to cut staff numbers at its Irish operations by 200 to 250, mainly in the manufacturing, operations and customer support areas.
APC employs 680 in Ireland, including 550 in Galway and just over 100 in Castlebar, with the remainder in Dublin.
The company has confirmed that all manufacturing is to cease at its Galway plant and will be consolidated at its Castlebar factory. It says employment there is likely to rise, but gave no specific figures.
The Galway plant will continue to be a centre for research and development, information technology, sales and customer support. APC is also consolidating and redeploying to other countries in the Middle East and Africa to reduce costs and improve efficiency.
APC has been in Galway since 1994 when it moved into the former Digital plant at Ballybrit on the eastern edge of Galway city. Workers leaving the plant at lunchtime said they were disappointed and upset by the sudden news that almost half of the workforce is to be made redundant.