Eircell was the first mobile phone operator in Ireland, and as of 2001 still commands a majority (around 60%) of the market with its billed and prepaid ("Ready to Go") products. Eircell is a sister company of Eircom, the primary land-based Irish telecoms company. Launched in 1985, the company has since grown to handle in excess of 6,000,000 calls and 1,000,000 SMS messages by 1.5m customers daily

However, this rapid expansion has caused the network to experience severe overcrowding, and even as of writing, it is often difficult to make a call at peak times (especially lunchtime), and capacity for WAP access is extremely poor. Competitors Esat Digifone and Meteor have of course taken advantage of high-profile incidents where the entire network has been brought down for days. Eircell responded on one such occasion by giving all its customers unlimited free SMS messages for the duration of the downtime (with the added side effect of popularising text messaging even further, of course).

Eircell's marketing strategies involve blanket advertising and promotions, such as giving free SMS messages on Christmas Day, Valentine's Day, and others. The company also currently has the highest coverage rate in Ireland; not surprising considering the opportunity it has had to erect masts during years of public obliviousness to their supposed dangers. This is a luxury its competitors have had to do without.

On May 13, 2001, Eircell became a subsidiary of UK mobile phone giant Vodafone, the largest mobile telecoms company in the world. This has lead to consolidation of roaming charges and tariffs in Europe, but has been the subject of much debate in Ireland.