ESB is taking a 50% stake in the Neart na Gaoithe offshore wind farm project in Scotland from French power group EDF Renewables.
The Neart na Gaoithe project, off the coast of Fife in the North Sea, has a capacity of about 450 megawatts of low carbon energy and will offset over 400,000 tonnes of carbon emissions each year.
Construction of components for the wind farm is now underway.
The ESB said that offshore construction will start in June 2020 and full commissioning will complete in 2023.
Once operational, the wind farm will generate enough electricity to power more than 375,000 households each year, or 4% of Scotland's electricity consumption.
Pat O'Doherty, chief executive of ESB, said the deal with EDF represents another key milestone in the company's investment in offshore wind.
"Our 50% stake in Neart na Gaoithe fits entirely with ESB's Brighter Future strategy to build a balanced low carbon generation portfolio of scale," Mr O'Doherty said.
Pat O'Doherty said that offshore wind is one of the main technologies underpinning the clean electricity systems that will power societies into the future.
"This investment in the Neart na Gaoithe project builds on significant ESB involvement in offshore wind off the Irish coast as ESB develops its experience to assist Ireland deliver its Climate Action Plan," he added.
EDF, which said it had raised $2 billion via the debt markets, said the offshore windfarm would be its largest in Britain to date.