Marseille have signed Argentina defender Leonardo Balerdi from Borussia Dortmund, both clubs announced on Tuesday.
In a statement, the clubs said Marseille had signed the 21-year-old on a one-season loan deal with an option to buy.
French media report Marseille will have to spend €15 million if they do wish to buy the centre-back before the end of next season.
Dortmund's sporting director Michael Zorc said in a statement Balerdi had approached the club with a transfer request in the hope of getting more playing time.
Balerdi, who played eight times for Dortmund since signing for Boca Juniors in 2019, is expected to join his new club in Bavaria late on Tuesday or Wednesday, before their friendly with German fourth division side SV Heimstetten.
He is Marseille's second recruit of the summer following the arrival of midfielder Pape Gueye, another promising 21-year-old, from Le Havre.
The signing of Balerdi will please coach Andre Villas-Boas, whose team finished second in Ligue 1 last season to reach the Champions League but needed strengthening in central defence.
Earlier on Tuesday, Marseille and Bayern Munich jointly announced they would face off in a friendly on 31 July, ahead of the Bundesliga champions restarting their Champions League campaign next month.