The 27-year-old has 17 international caps for the Netherlands as well as Champions League experience with PSV. He will slot in well in Stoke's back four - a left-back was the priority on Mark Hughes' summer shopping list.
Left-back is a slot Stoke had problems with all last season. After Marc Wilson broke his leg, Ryan Shotton was drafted in but the hometown boy never seemed able to keep up with the pace of Premier League football.
Pieters can play at left-back or in centre midfield, but the central midfield partnership of Robert Huth and Ryan Shawcross was one of the main reasons Stoke had the best defence in the Premier League up until Christmas last year.
The Dutchman, alongside Robert Huth and Ryan Shawcross, could give Stoke the stability they were lacking last season.
This is Hughes's first signing as Stoke manager and it couldn't have come sooner as some Potters fans were growing impatient. However, the former QPR boss did re-sign Jermaine Pennant to the club on a one-year-deal, a decision that received mixed views from supporters.
Stoke have also been linked with Blackburn's Martin Olsson as they continue to strengthen their back four.
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