Following the loan move of John Guidetti from Manchester City until the end of the season, the midfielder has joined the Potters on a full-time basis to comply with league rules
The midfielder had been on a season-long loan but the club needed to reduce their temporary deals to two after John Guidetti joined on loan from Manchester City earlier in the day.
Ireland now links up with Mark Hughes on a full-time basis for the second time, following a period together at the Etihad Stadium, and the Potters boss spoke of his happiness with the move.
"Stephen is a talented footballer and has shown what he’s capable of since he joined us," Mark Hughes told the club's official website.
"We’re delighted to have made his switch a permanent arrangement as it also gives us the opportunity to bring in another player on loan if necessary."
Ireland has made 16 appearances for Stoke this season, scoring three goals.