The 25-year old Irish attacker has been heavily linked with a move away from The Hawthorns in recent months and it has now been confirmed that he has signed a three-year deal with Forest.
Cox, who has joined for an undisclosed fee, is looking forward to a new challenge after three seasons with the Baggies where he struggled to make a massive impact.
"I'm delighted to have signed a deal with Forest and I'm really looking forward to the task ahead," he told the club's official website.
"The history of the club sells itself and I had a chat with [manager] Sean O'Driscoll and liked what he had to say.
"I also met the chairman the other day and had a good look around the facilities and can tell it's a club going forward.
"One of the most important things for me were the assurances I was given by the owners. I've seen enough in football where owners come into the clubs, have a little flutter and then go away.
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