Stoke have not revealed the length of the contract signed or the value of the transfer fee involved.
"There is nothing better than to have strong competition in all areas of the squad and Michael's arrival will give us that in the wide positions," he told the club's official website.
"I've long been an admirer of Michael, not only in terms of him being a provider, but also the fact that he gets his share of goals.
"Our two wingers, Matthew Etherington and Jermaine Pennant, have been brilliant for this football club over the past few years, but they went off the boil in terms of goalscoring last season, so we wanted to address that.
"Competition for places will bring the best out of them again and that is what Michael's presence will give us in that area."