Manchester City signed Belgian winger Jeremy Doku from French club Rennes on a five-year deal on Thursday.
Doku, 21, will reportedly cost the European champions £55 million.
"This is a great day for me, both personally and professionally," Doku said in a City statement.
"Manchester City are the best team in world football, so to be joining them is something very special for me and my family.
"I am a young player with so much learning and improving to do. Working with Pep (Guardiola) and his staff, and playing alongside these work-class players, will make me a much better player."
Doku scored 12 goals in 92 appearances for Rennes after making his breakthrough as a teenager with Anderlecht in his homeland.
He becomes City's third signing of the transfer window after Croatian international duo Mateo Kovacic and Josko Gvardiol.
The treble winners were in the market for a winger to replace the departed Riyad Mahrez, who joined Saudi side Al-Ahli.
City are also expected to add a midfielder before the window shuts on 1 September to cover the absence of Kevin De Bruyne, who is set to miss up to four months due to a hamstring injury.
Wolves' Matheus Nunes and Crystal Palace's Eberechi Eze are reportedly targets after interest in West Ham's Lucas Paqueta collapsed due to a Football Association investigation into a possible breach of betting regulations by the Brazilian.
