The licence area covers a potential 950,000 listeners aged 15 and above.
GCap faced competition from its biggest rival Emap and its Kerrang! radio brand, as well as two other rock music-focused bids from Absolute Radio's Dave FM, and UK Media and Radio Wales' Wicked FM.
The four other bidders were CanWest with Original FM; UTV Radio with AllTalk FM; Town & Country Radio with South Wales Radio; and Guardian Media Group Radio with Variety FM.
Nick Davidson, managing director of Xfm, said: "We are over-the-moon with the announcement and can't wait to get moving on bringing everything great about Xfm to such a fantastic area with a strong musical heritage. We received so much support from the local people when we were putting the bid together and as a local myself I can't wait to be able to tune into a station that plays great new music."
Xfm recruited Manic Street Preachers' outspoken bassist Nicky Wire to chair its advisory board for the bid, while fellow Welsh musicians Kelly Jones of Stereophonics and former Catatonia singer Cerys Matthews lent their support to the bid process.