Alessia Russo will leave Manchester United at the end of June, with the England striker poised to seal a move to Women's Super League rivals Arsenal.
The Gunners made a world-record bid to land the European Championship-winning Lioness in January but she will be available for free when her United contract expires on June 30.
Russo, 24, tweeted: "It’s been the hardest decision I’ve ever had to make.
"Manchester United Women, thank you for everything."
The striker joined the Red Devils in 2020 after time spent in the United States with the North Carolina Tar Heels.
She went on to make 59 appearances for United, scoring 26 times, and played a key role in a historic season for the club in 2022-23.
Marc Skinner's side finished second in the WSL, reached the Women's FA Cup final and sealed Champions League qualification for the first time, with Russo notching 13 goals in 24 games.
A statement from United said: "Everyone at the football club would like to thank Alessia for her service and wish her luck for the future."
