The right-back joins from Tottenham on a five-year deal and has opted to take the number two shirt.
He becomes City’s third signing of the summer, following in the footsteps of Bernardo Silva and Ederson.
“I am thrilled to be signing for City and can’t wait to get started,” Walker said.
“Pep Guardiola is one of the most respected managers in the world and I feel he can help me take my game to a new level.”
Txiki Begiristain, the Club’s Director of Football, added: “Kyle is a fine full-back, one capable of producing quality at both ends of the pitch.
“We’ve followed his progress at Tottenham and have been really impressed by how he has developed. He is now one of the best right-backs in the Premier League and justifiably an England regular.
“I am sure he will be a success at Manchester City this season and beyond.”
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Walker began his career at Sheffield United, where he spent a short period on loan at Northampton before returning to Bramall Lane and impressing in the final few games of the season 2008-09 season as the Blades made the Championship playoffs.
The 27-year-old signed for Tottenham that summer and was immediately loaned back to Sheffield United as part of the deal to ensure his progress continued.
But after impressing in the opening months of the 2009/10 season, he was recalled to Spurs and made two senior appearances.
Further loan moves followed, to QPR and Aston Villa, in a bid to secure further first-team experience but in 2011 he forced his way into the Spurs side and became their first-choice right-back.
In 2012, he was rewarded for a fine season by picking up the PFA Young Player of the Year award and has twice been named in the PFA Team of the Year.
He made 228 appearances for Tottenham in all competitions, scoring four goals, and last season helped them to second in the table, their highest league finish in the Premier League era.
His England debut came in the 1-0 win over Spain in 2011. He has 27 caps in total, with his most recent appearance coming as a second-half substitute in the 3-2 defeat to France at the Stade de France.
Everyone at Manchester City would like to wish Kyle the best of luck as he begins the next stage of his career here at the Etihad Stadium.