The right back becomes Forest's 22nd signing this summer.
"Nottingham Forest is delighted to confirm the signing of Ivory Coast captain Serge Aurier, subject to Visa approval," the club said in a statement.
Aurier previously played in the Premier League during a four-year spell with Tottenham Hotspur before moving to Villarreal in October last year.
He made 24 appearances for the Spanish side last season, including five times in the Champions League as they reached the last four of the competition.
Steve Cooper's Forest, 19th in the league standings with four points from six games, travel to Leeds United on Monday.