Apple is to invest €850 million developing a new data centre in Co Galway.
The centre will be built on a greenfield site in Derrydonnell, near Athenry.
The company says 300 jobs will be created over the multiple phases of the development process, from construction to operation.
It is understood that around 100 jobs will be created when the centre is fully operational.
The new centre is part of a worldwide investment announced by Apple, with plans for a similar facility announced for Denmark.
The two data centres are expected to begin operations in 2017.
Data centres are used by Apple to operate services such as its online music and app stores and to host information uploaded by users to the company's cloud facilities.
The announcement is viewed as an indicator of the company's long-term plans in Ireland.
It follows recent controversies about Apple's financial arrangements in Ireland and Government plans to phase out the "double Irish" arrangement, which allowed companies to reduce their tax liabilities.
The investment, backed by the IDA and supported by the Government, follows a number of meetings between Minister for Jobs Richard Bruton and senior Apple executives both in Ireland and in the US.
The Irish climate is seen as ideal for data centres, as the generally predictable temperatures ensure that companies can minimise the cost of cooling the vast amount of equipment used to store information in these facilities.
Several other companies, including Ericsson, Microsoft and Google, have expanded their data capabilities in Ireland in recent years, but the investment of €850m by Apple is significantly larger than previous announcements.
The company already employs 4,100 people in Ireland, the majority at its European Headquarters in Cork.
The company said the new facilities in Galway and Denmark will run entirely on clean, renewable energy sources.
The Athenry facility will be built on land owned by Coillte.
Today, Apple shares closed at $133 - a record high.
Taoiseach Enda Kenny said: "It is a very significant investment in the West of Ireland and is fantastic news for Athenry with significant knock-on benefits for the region.
"As the Government works to secure recovery and see it spread to every part of the country, today's announcement is another extremely positive step in the right direction."
Minister Bruton said: "At the heart of our jobs plan for 2015 is accelerating jobs growth in every region of the country."
He said the announcement "is a huge boost for the west and a great example of what is possible with the right policies".
In a statement, Apple CEO Tim Cook said: "This significant new investment represents Apple's biggest project in Europe to date.
"We're thrilled to be expanding our operations, creating hundreds of local jobs and introducing some of our most advanced green building designs yet."