Sergio Conceicao has left Nantes and agreed to take over at Porto, according to a statement from the Ligue 1 club.
The former Portugal international had a deal with the French side until 2020, but showed an "irreversible willingness" to replace Nuno Espirito Santo - now in charge at Wolves.
Conceicao took over last December and guided Nantes away from the lower reaches of the table to a seventh-place finish.
But the club announced on Tuesday that he and three of his staff had departed for Porto, who finished second in the Primeira Liga.
Nantes president Waldemar Kita said: "I had made sure to give him all the means to continue the adventure. I wish him good luck.
"Now we are looking for a new coach and there is no shortage of proposals, proof that FC Nantes is attractive."