The married man in his early 60s from Rutherglen, South Lanarkshire, won £1,659,372 on a £1 spin playing William Hill's Pig Wizard on his tablet device.
He and his wife toasted their win with champagne before he quit his factory job and promised to take her to Las Vegas.
"I couldn't believe it when I won it," said the man, who is remaining anonymous.
"I kept saying over and over again, 'This can't be true'. I didn't sleep for two whole nights and my wife was climbing the walls as we waited over the bank holiday to see the money in our account.
"We are just so happy and enjoyed a nice bottle of Dom Perignon to celebrate. I was nearing retirement but now I can retire a wee bit early and put my feet up."
The father-of-one will ensure his grown-up child is "well looked after" and plans to give thousands away to close family and friends. "We've got a lovely family and to think I can make such a difference to their lives just by playing a game for a bit of fun. It is just incredible."
He added: "I will head off to Vegas with my wife but I will make sure I won't spend too much."
William Hill said it was its biggest casino win to date.