Foras na Gaeilge has said it will cut the number of Irish language groups for which it provides "core funding" across the island of Ireland from 19 to six.
None of the six successful organisations is currently based in Northern Ireland.
Pobal, Iontabhas Ultach, Forbairt Feirste and Altram will lose a significant portion of their budgets.
They provide support for the language in business, education and the arts in Northern Ireland.
Foras said the bodies it plans to fund in the future will promote the language and provide services on an all-island basis.
It agreed the plan at a board meeting in Dublin.
Chief executive of Foras, Ferdie Mac an Fhailigh, said: "`Foras na Gaeilge recognises that the six months ahead will be a difficult period for organisations whose funding from Foras na Gaeilge will come to an end following this decision.
"And every effort will be made to ensure that the Irish-language community will not suffer as a result of these huge changes, and that the important work being done by organisations which were not selected will continue."
Foras na Gaeilge had to rationalise because a significant proportion of the money it gave out was being spent on salaries.
In 2008, it allocated 40% of its budget, 8m euros (Â£6.6m), to the 19 "core-funded" organisations. They used more than half of that to pay salaries.
In subsequent years, the salary bill continued to increase and by 2011, close to 60% of grant money awarded was being spent on pay.
In a report drawn up as part of the rationalisation plan Foras said: `"Based on the above trend, and were it to continue, most of the funding would be spent on wages and there would be a risk to service provision."
Foras na Gaeilge was set up in the wake of the Good Friday Agreement to promote the language. It is funded by the Irish government and the Northern Ireland Executive. Its own budget has been significantly reduced in recent years.
The rationalisation plan was approved at a meeting of the language body of the North South Ministerial Council in July last year.
The meeting was attended by Culture Minister Caral NÃ­ ChuilÃ­n and her counterpart from the Republic of Ireland, Jimmy Deenihan TD, Minister for Arts, Heritage and the Gaeltacht.
Two organisations in Northern Ireland that receive core funding from Foras na Gaeilge will be protected from the changes.
Radio Failte, an Irish language station based in Belfast, and an t-Aisionad, an Irish education resources centre based at St Mary's teacher training college on the Falls Road will continue to be funded under separate arrangements.
The changes in funding arrangements will take effect from July.

The Huntsman spider was spotted by staff at a manufacturing firm in Dumbarton on Friday.
They called in the Scottish SPCA amid concerns that it could be poisonous.
The animal charity contacted an arachnid specialist who helped identify the spider, which can give a painful bite. The Huntsman is being cared for while a suitable home is sought.
Scottish SPCA Animal Rescue Officer Emma Bonner, who dealt with the incident, said: "We were called to a manufacturing business on Stirling Road, Dumbarton, on Friday morning after we received reports of a large spider.
"When I arrived one of the employees had managed to get the spider inside a clear bag within a container. We didn't know if it was venomous."
The spider was passed to Scottish SPCA Ch Insp Fiona Henderson who contacted a specialist.
Ch Insp Henderson said: "An arachnid expert identified it as a Huntsman spider. We believe that due to a yellow stripe on its abdomen that the spider is female.
"It would be hard to say where it is from exactly due to the fact it arrived here in a shipping container.
"It must be a tough little spider as it has done well to survive living in a cold container for so long before arriving in Scotland."
Ch Insp Henderson added: "Because it's a Huntsman it's not native to this country so we can't release the spider anywhere in Scotland.
"If there are any bacteria or bugs that the spider is carrying that we are not aware of then it could introduce those to other species.
"The spider appears in good condition and is already an adult so we are going to try to find a specialist home for it."
Four Irish language organisations in Northern Ireland are to lose key funding under a rationalisation plan.
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A giant spider common in Australia, Africa and Asia, has been found inside a shipping container in Scotland.