The 27-year-old has been talking to AC Milan with the Serie A Club in recent days that needs a replacement for Theo Hernandez, who became a member of Saudi Club Al-Hilal.
According to Fabrizio Romano, an agreement has now been reached between Brighton and Milan for the Estupinan transfer.
It is clear that the reimbursement will be € 17 million plus € 2 million in add-ons, for the Ecuador International that made 36 performances in all competitions last season.
Brighton has already succeeded in signing a replacement for Estupinan and to sign the Cuyper from Club Brugge earlier in the summer.