Formal consent has been granted for neighbouring projects by Moray Offshore Renewables Limited and Beatrice Offshore Windfarm for a total of 326 wind turbines.
The developments in the Outer Moray Firth, 14 miles off the coast of Caithness, will together be capable of generating up to 1,866MW of electricity. If constructed, the combined schemes will be more than double the scale of the 175-turbine London Array, in the Thames Estuary.
Energy minister Fergus Ewing said: “These wind farms alone could generate gross value worth up to £2.5 billion over their lifetime and generate up to 4,600 jobs during peak construction and up to 580 once in operation.
“Offshore wind has been delayed by the process of the UK government’s electricity market reform, but these two consents today offer tangible progress towards real investment opportunity in Scotland.
“The Scottish Government is committed to the successful and sustainable development of an offshore wind sector, which could lead to a potential inward investment of £30bn and support up to 28,000 direct jobs and a further 20,000 indirect jobs, generating up to £7.1bn for the Scottish economy.
“The Scottish Government wants to see the right developments in the right places and Scottish planning policy is clear that the design and location of any onshore and offshore wind farm should reflect the scale and character of the landscape or seascape and should be considered environmentally acceptable.”
Environmental campaigners have welcomed the announcement as a step forward in the fight against global warming, but they also highlighted the need for strict measures to protect nature.
Dr Richard Dixon, director of Friends of the Earth Scotland, said: “Offshore wind is relatively new in Scottish waters and these schemes will need careful monitoring as they are built and operated to ensure that the impacts on wildlife are minimised.
“As a global leader, Scotland can create green electricity, reduce climate emissions and generate new jobs.”
But a leading conservation group has attacked the proposals, saying the size of development poses “too great a threat” to wildlife. RSPB Scotland, which backs offshore wind development but has previously encouraged scaling back in the Moray Firth, voiced fears over the dangers posed to key seabird species.
“Some seabird populations in this area are already under massive pressure and in dramatic decline,” the charity said. “These developments could tip them even further over the edge.”
Anti-wind campaigners have also hit out at the plans, accusing the government of granting “an irresponsible consent for an unsustainable technology”.
Linda Holt, spokeswoman for Scotland Against Spin, said: “Offshore wind is the most expensive form of energy generation that we have and the least cost-effective way of reducing our carbon emissions.”
She said the announcement was “no more than a political stunt” by the Scottish Government.
Chief executive of the Scottish Fishermen’s Federation Bertie Armstrong said: “It is absolutely essential that the fishing industry continues to be fully consulted during the complicated planning and licensing processes.”