The company launched in July 2005 and provides 2G GSM, 3G UMTS, 4G LTE and 5G NR mobile phone services.

Three launched on 26 July 2005 as Ireland's fourth mobile network operator behind Vodafone, O2 and Meteor (now Eir).

As per its latest released mid year statements about 56 per cent of Three's 554,000 registered subscribers are considered active.

[1] On 24 June 2013, it was announced that Hutchison would acquire Telefónica's Irish mobile operations, O2 for €780 million, to be merged into Three Ireland upon completion of the deal.

[6] The agreement was terminated following the O2 merger In November 2012, Three was awarded LTE spectrum by auction, along with the three other incumbent network operators.

[8] In March 2014, Three expanded their 4G coverage to Ashbourne, Bray, Carlow, Dunmore East, Kilkenny, Leixlip, Lusk, Rush, Skerries, Swords and Tullamore.

Three was named Ireland's fastest mobile network by Ookla for Q3–Q4 2020, with an average download speed of 33.99 Mbit/s.

The value proposition for the brand has been offering unlimited call, text and data for a low fixed monthly price.