Guerrero was part of the squad that won Spain's first World Cup last month, making three substitute appearances. The financial details and length of contract were not disclosed.

The central midfielder, who has 16 caps, joined Atletico in 2022 - winning the Queen's Cup last season.

"Irene is a World Cup winner whose quality is an excellent addition to our team," United coach Marc Skinner said.

"The experience she brings, both domestically and internationally, will be key as we pursue success across the multiple competitions we face this season. We are delighted to bring a player of Irene's stature to Manchester United Women."

United, who finished second in the league last year, open the new WSL campaign at Aston Villa on October 1.