Forest appoint Pereira as fourth boss this season
Former Wolves boss Pereira agreed an 18-month contract with Forest, who sacked Sean Dyche earlier this week.
Nuno Espirito Santo and Ange Postecoglou have also been dismissed by Forest during a turbulent campaign.
"Nottingham Forest is delighted to confirm that Vitor Pereira has been appointed as head coach on an 18-month deal," a club statement said.
Pereira will be tasked with hauling Forest away from the Premier League relegation zone.
Dyche was axed following Wednesday's 0-0 draw against bottom-of-the-table Wolves.