The 27-year-old Irish midfielder joined Stoke last September in a move that saw him reunited with Mark Hughes, his former manager at Manchester City.

"Stephen is a talented footballer and has shown what he's capable of since he joined us," Hughes told the Stoke 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 made 176 appearances for City before joining Villa in August 2010 in a part-exchange deal that saw England midfielder James Milner move in the opposite direction.

He has made 16 appearances for Stoke in all competitions this season, scoring three goals.

Stoke also announced on Tuesday that they have signed 21-year-old Swedish striker John Guidetti on loan from City until the end of the season.