U105 was picked from a field of 11 applicants, including Emap, GWR, Celador, Independent News & Media, and The Wireless Group.
The station is planning to be on air by early 2005 and will spend more than £2m on a marketing campaign that will link it to the UTV brand.
As well as covering around 750,000 adults aged 15-plus in the Belfast area, it will be available to the whole of Northern Ireland on Freeview. The licence will run for 12 years.
Roy Bailie, chairman of U105, said: "U105 will appeal primarily to those aged over 45 living in Belfast and the surrounding area, an audience currently underserved by existing stations."
He said that seven out of 10 listeners in this age group do not currently listen to local commercial radio, and that U105 planned to change that.
The win puts UTV up against BBC Radio Ulster as well as CN Group's City Beat and Scottish Radio Holdings' Cool FM.
UTV holds the ITV franchise for Northern Ireland and has a radio division, as well as internet service provider operation. It owns radio stations in Dublin, Cork, Limerick and Liverpool.
It bought LMFM, an independent radio station serving the counties of Louth and Meath in the Republic of Ireland, in February.
The company yesterday announced pre-tax profits for 2004 of £13.9m, up from £9.5m in 2003.
Ofcom also announced that the new radio licence for Cornwall had been won by Atlantic Broadcasting's Atlantic FM, which beat seven other applicants.
The service will cover around 410,000 adults aged 15-plus and target listeners aged 25-54.
Although unlikely to be confused with it, U-105 was also a World War II U-boat, which was sunk pff Dakar in 1943.
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