Borussia Dortmund have signed Swiss defender Manuel Akanji from Basel.
The Bundesliga club says the 22-year-old signed a deal through to June 2022.
Dortmund sporting director Michael Zorc said: "Manuel's performances put him on the radar of a number of top European clubs, and we're delighted that he's chosen to join us.
"He has already demonstrated at international and Champions League level that he can play at the highest level in Europe."
Akanji helped Basel win the Swiss league in 2016 and domestic double last year after joining in 2015.
He scored five goals in 42 league appearances and also made four appearances for Switzerland.
Kicker magazine reports Dortmund are paying £16m (€18m), potentially rising to more than £17.8m (€20m), for the transfer.