Barcelona from Manchester City, the Women's Super League club said on Wednesday, with British media reporting the deal was for a world-record fee of around 350,000 pounds ($401,170).
The previous world record women's transfer stood at a fee in excess of 250,000 pounds, which Chelsea had paid in 2020 to sign Denmark's Pernille Harder from VfL Wolfsburg.
Walsh, 25, who joined City in 2014 as a teenager and played 211 matches in all competitions for them, lifted eight trophies with the club in as many years.
She was in the final year of her contract at City, who had reportedly rejected previous bids from Spanish champions Barca. A versatile player who can operate as a playmaker or defensive midfielder, Walsh was part of the England side that captured the woman's European Championship this year and was part of the team of the tournament. "Everybody at Manchester City would like to thank Keira for her contributions during her time at the club and wish her all the best for the future," City said in a statement.