The Cork County Board have announced that their sponsorship partnership with O2 will end on 31 December this year.
Bob Ryan, chairman of the Cork County Board, said: “We are obviously very sorry to lose O2 as sponsors of Cork GAA after 15 mutually successful years.
“The County Board officers, our hurling and football players, our team managements, and our supporters, have enjoyed an excellent relationship with O2, and with its executives and representatives.
“We wish to thank them for their partnership and generous support over the years.
"We are currently in negotiations with a number of interested parties about the sponsorship of Cork GAA from 2013 onwards."
No replacement sponsor has been announced as yet.
O2's marketing director Eugene Mitchel described the company's relationship with Cork as "tremendous" and thanked the Cork board, players, management and supporters.