Three has entered into an agreement with Telefonica to buy its O2 business in Ireland for €780m (£665.1m).
A further additional payment of €70 million is payable dependent upon achievement of agreed financial targets.
The acquisition of O2 will take Three's market share in Ireland to 37.5%, making it the biggest mobile operator in Ireland, and bring subscriber numbers to 2m active users.
The two companies had combined revenues of €803m in 2012, which compares to Three's revenue of €174m in 2012 on a standalone basis.
In a statement Three Ireland’s owner Hutchinson Whampoa said the deal will provide Three with ‘the scale and financial strength necessary to compete even more aggressively in the market to the benefit of consumers.’
It added that it will leave Three ‘the number one player in the Irish market’ promising plans to invest in the creation of ‘a state of the art network including 4G/LTE over the next number of years’.
Commenting on the deal Robert Finnegan, CEO of Three Ireland said, ‘Three is very pleased to have agreed to acquire O2 Ireland, a business whose strengths complement ours very well. Since market entry in 2005, Three Ireland has grown organically through innovation, competitive pricing and quality customer offerings. As an ambitious competitor in the market we have been looking at ways to increase customer numbers and grow market share, and acquisition was the natural next step.
‘Our combined 37.5% market share gives us the scale and financial strength to compete even more aggressively in the market to the benefit of consumers. Our ability to invest coupled with the combined subscriber base will create new competitive dynamics in the Irish telecoms market.
He added: ‘Increasing access to high-quality high-speed networks for Irish businesses and consumers is an essential part of our national economic recovery. This deal will allow significant investment to be made in building a state of the art network. The combined network will also deliver very real benefits to customers outside the major urban areas as the increased scale will allow Three to extend its rural network investment programme beyond 2014.’