The first of 160 wind turbines has been installed at the North Wales Gwynt y Môr Offshore Wind Farm, the largest renewables project under construction by RWE npower renewables.
Once fully operational, the wind farm will be capable of generating enough energy from the wind to power around a third of the total number of households in Wales.
The 3.6 megawatt Siemens turbine was fitted more than eight miles off the North Wales coast in Liverpool Bay, using the SeaJack vessel.
RWE npower renewables' Gwynt y Môr project director, Toby Edmonds said: "We're very pleased to be able to mark such a significant milestone in the construction of our flagship Gwynt y Môr Offshore Wind Farm, the largest renewables project under construction in the RWE portfolio.
"Energy generation from our own domestic, limitless and renewable sources has been demonstrated to be of such importance to Wales and the UK's future energy security, and Gwynt y Môr's turbines will soon begin to make a significant contribution to that generation capacity.
"Each turbine consists of a tower in two sections, a nacelle, a hub and three blades and takes approximately 24 hours to install.
"SeaJack can carry three sets of components at a time and is scheduled to return to the Port of Mostyn every nine days to pick up more components.
"A second jack up vessel, SeaWorker will arrive on the project later in the summer and turbine installation is due to continue into 2014."
At 576MW, Gwynt y Môr is one of the largest offshore wind farms currently in construction in Europe.
It is a shared investment between partners RWE Innogy, Stadtwerke München GmbH and Siemens.