"I cannot thank Birmingham City enough for what the club has done for me, not only this season, but since I came to the club when I was seven years old," Bellingham told Dortmund's website.
"Now I'm really excited to play in one of the biggest clubs in Europe. Dortmund's style, and especially the way they help young players improve, made the decision very easy for me personally and for my whole family.
"I can not wait to play in one of the most beautiful stadiums in the world, hopefully in front of over 80,000 spectators as soon as possible."
— Borussia Dortmund (@BVB) July 20, 2020