Dubbed the 'Mini Messi', 22-year-old Kirby was one of the stars of England's successful Women's World Cup campaign and moves from Reading, where she has played since she was eight.
In a statement, Reading said all the money would allow them to keep their team " progressing in their current manner"
"It goes without saying that I'm very excited about moving to Chelsea, and I can't wait to get started at a new club," Kirby said
"But at the same time I am leaving behind so many memories at Reading.
"When I joined the club aged eight, I could never have imagined where it would take me
To have success with all my team-mates at Reading, played for England in the World Cup and now make this move, it's all a little bit surreal to be honest."
Kirby has signed a three-and-a-half-year contract and will be available to face Bristol Academy this weekend.
Source : PA
Source: PA