The full-back arrives on a three-year deal from Olympique Lyonnais, whom she won the Champions League with last season.
A 46-cap England international, Greenwood is City’s fifth signing of the summer, following in the footsteps of former Lyon team-mate Lucy Bronze and will wear the number 27 shirt.
“I’m so excited to get going,” she said after completing her move.
“It’s been a crazy and unforgettable few weeks, but I just can’t wait to get started and bring that winning feeling to City.”
You can check out the first photos of Alex in a City shirt in the gallery below.