Eir has said it will begin switching off its 3G mobile network from October.
First launched in Ireland in 2007, 3G allowed for high-speed mobile internet connectivity for the first time.
Eir's predecessor, Eircom, was awarded a 3G licence in 2009.
However the technology has since been superceded by 4G and 5G, which is capable of far faster and more reliable connectivity.
Eir said the switch-off was part of its "ongoing mobile network evolution" and would help it continue to develop its 4G and 5G networks.
It said the move would have no impact on the vast majority of its customers, who are already using faster connections.
It said it would directly contact its customers who are currently using 3G-only services.
The switch-off will begin on 1st October and will progress on a phased basis over a number of weeks, it said.
