The 20 year-old Tottenham Hotspur forward was hot property following an impressive loan stint in League One with Leyton Orient last term, where he scored eight goals and provided 10 assists as the Os made the Play-Off Final.
Although several Championship sides were keen on his signature, Stoke got the deal over the line.
Donley said: “I had a few teams after me but I decided on Stoke when the gaffer [Mark Robins] called while I was away on tour with Spurs.
“The way he wants to play, both in terms of attacking and defending, definitely suits me.
“I’ve heard a lot about the coaching staff and how the manager improves young players. You can see that in the history he's had in working with different teams.
“I'm very much a team player, Stoke City fans can know I’ll work really hard, whether that’s defensively or making options to receive the ball to play forward.
“I enjoyed a really positive loan last year, I know about the pressure of men’s football now and how people look to you to contribute in games. I took to that pressure well and I want to carry that on here at Stoke City."
The Antrim-born footballer switched allegiances from England to Northern Ireland earlier this year, after winning caps at Under 17 and Under 19 level for the Three Lions. He made his senior debut for Michael O’Neill men against Switzerland in March and has since won two more caps.