Sinn Fein and some independents voted against the plans, Labour abstained.
Several Fianna Fail councillors voted in favour of the plans for the turbines which were to be located between Lough Derg and the N15 Donegal Town-Ballybofey Road.
Councillors voted on the issue today – with 15 voting in favour, five against with two abstentions.
However because two-thirds of councillors failed to back the development (21 were required) the motion fell.
The application was made by Eco Wind Power Limited from Santry, Dublin.
The turbines would have been 70 metres high – with a rotar blade mesauring 84 metres.
A large number of environmental groups had opposed the plans which had been first submitted in 2010.
County planners had recommended permission be granted subject to a number of conditions.