Cooper's switch to Kingsholm will see him have to fight it out with Scottish scrum half Rory Lawson and former Munster and Bourgoin half back Mike Prendergast. Gloucester's England cap Peter Richards is moving on to London Irish.
"When you come from Wales there are certain rugby clubs in England that you immediately associate with history, pride and tradition and Gloucester is one of the biggest," said Cooper. "There is nothing half-hearted about what they are trying to achieve in the Guinness Premiership and Heineken Cup.
"Their coaching staff are amazingly driven, the squad that is being assembled is one of the best in Europe and I couldn't pass up the opportunity to be involved with such a progressive and talented set-up.
"This is the opportunity of a lifetime for me and Dean Ryan's ambition to make Gloucester the dominant force in club rugby is something I want to be part of.
"I know a lot of people say it, but when you see the training facilities at Hartpury College and understand the direction in which the club is heading, my mind was made up. I think this will be a fantastic move."