Planning approval has been granted for the North-South Electricity Interconnector, Infrastructure Minister Nichola Mallon has announced.
The project will create a 138km overhead electricity line stretching from County Tyrone to County Meath.
Previous applications have been quashed by court rulings, with the decision returning to the department.
Ms Mallon said the proposal will enhance network stability and bring economic benefits.
The minister said: “Following the quashing of the previous decision, I have carefully reconsidered the proposal and the up-to-date environmental information and have concluded that planning permission should be granted for the development which remains of strategic importance for our island economy.”
Planning approval for the section in the Republic of Ireland was given in 2016 and later upheld in the Irish Supreme Court after legal challenges.
“The North-South Electricity Interconnector remains crucial to handling growing demand across the electricity transmission systems across the island of Ireland, promoting greater competition within the Single Electricity Market (SEM) for wholesale electricity trading and to protecting security of supply,” Ms Mallon continued.
The approval is for the building of a single circuit 400kV electricity line consisting of 102 towers over 34.1kms in length from Moy in County Tyrone to Crossreagh in County Armagh.
From there, a further stretch extends to the townland of Crossbane.
There were more than 6,000 letters of objection to the original proposal and more than 3,500 since a consolidated environmental statement was submitted.
Jim Lennon, chair of Safe Electricity Armagh and Tyrone, said his group was disappointed by what he called a “premature decision” ahead of the publication of the Energy Strategy for Northern Ireland next year.
“Why rush a decision that will live with us for the next 40 years?” he questioned.
“We are not anti-development, but we believe any proposal must be evidence-led and properly take account of the impact it will have on local people,” he added.
SONI, which operates the electricity grid in Northern Ireland, welcomed the decision and said it would be a “catalyst for Northern Ireland’s response to climate change, reduce consumer costs and provide a long-term electricity supply”.
Managing Director Jo Aston described the project as “undoubtedly the most important infrastructure scheme on the island today” and said it would be a “key enabler for economic growth as Northern Ireland emerges from the Covid-19 pandemic”.
“This vital project has been in the planning system for more than a decade, including extensive consultation and two public inquiries, neither our economy, nor our climate can wait any longer,” she added.
Glyn Roberts, chief executive of Retail NI, said Monday’s decision was “excellent news for our economy”.
He added it will mean long-term lower energy bills for the organisation’s members and represented “an investment in the future of our energy infrastructure”.
“I hope that we will now see rapid progress for this vital project in Northern Ireland and no more unnecessary delays.”