The 28-year-old joins from Birmingham City, where she played for two-and-a-half years. She has signed a contract with Chelsea until May 2022.
Berger told chelseafc.com: ‘I’m excited. It’s something new, I’m looking forward to playing with one of the best clubs in the world right now.
‘First of all, I really like the league. Chelsea is one of the best so far since I’ve been in England and I think now is the right time to come and play for a big club. Chelsea felt like the right choice.’
Chelsea Women manager Emma Hayes says: ‘For the last two seasons Ann-Katrin has been the best goalkeeper in the league and having played both in Germany and France, she’s developed the experience which makes her ready for Chelsea.
‘She has the experience, pedigree and certainly the mentality to come in here and succeed and add to the glut of quality goalkeepers we have here. I look forward to seeing her in training with this group.
‘It is critical when you come to Chelsea that you have the experience to compete from day one. We’ve got quality goalkeepers in place and she will add to that. She has the discipline, desire and ambition to kick on with her career and Chelsea is the perfect place for her to achieve those ambitions.’