Up to 500 jobs are to go at the Molex manufacturing plant in Shannon, County Clare.
At a meeting with management this afternoon, workers were informed of the decision to close the facility by the end of next year.
According to the electronics manufacturer, the closure will be subject to an employee consultation process - but the closure is set to take place in a series of phases beginning in early 2020.
The company has had a facility in Shannon since 1971.
Announcing the closure, Molex claimed "the majority of products made at the Shannon facility have insufficient financial returns and growth potential".
In a statement, Business Minister Heather Humphreys said she was "bitterly disappointed" at the news.
She said: "My immediate thoughts are with the workers and their families at what is a very difficult time for them and for the wider Shannon area.
"I fully appreciate how important large-scale employers like this are to regional areas, which makes this company closure all the more difficult.”
The Government has pledged to do "everything possible" to help the affected staff.