ScottishPower Renewables' Kilgallioch development will straddle the border of South Ayrshire and Dumfries and Galloway.
The company has signed an agreement with Spanish firm Gamesa to supply turbines to the site near New Luce.
Delivery of the 96 turbines is expected to begin in February 2016.
The site is expected to be completed in early 2017.
Keith Anderson, CEO of ScottishPower Renewables, said: "Kilgallioch wind farm will become our second largest wind farm in the UK and this year marks a real milestone as we approach 2 GW of installed onshore wind capacity - enough to power more than one million homes.
"We are delighted to reach this agreement with Gamesa, and we look forward to work commencing on the site next month."
The firm has previously claimed the development could meet the energy needs of more than 130,000 homes and its construction will create about 200 jobs.
Meanwhile, SSE has confirmed that it has completed the sale of three Scottish wind farms to Blue Energy for an undisclosed sum.
Blue Energy will now have responsibility for constructing the Whiteside Hill and Blackcraig developments in Dumfries and Galloway, and Cour wind farm in Argyll. All three have planning consent.
The renewables firm behind plans for a major wind farm in the south of Scotland has confirmed that work will start on the site next month.