The Ivory Coast international's contract at Tottenham was cancelled in the summer and he has been looking for a new club after a four-year stint in north London.
The 29-year-old has now signed a one-year deal with Villarreal, who defeated Manchester United in the Europa League final on penalties in May.
A statement from the Spanish club read: "Villarreal CF have reached an agreement with Serge Aurier, who joins the Yellows as a free agent and will represent the Yellows this season, with the option of extending the link between both parties for two further campaigns.
"After completing his medical and signing his Villarreal contract, Aurier will head off to represent his country, Côte d'Ivoire, who have called him up for two World Cup qualifiers against Malawi (Friday 8th and Monday 11th October).
"The defender will join up with the Yellows after the international break and will be presented officially as a new Yellows player when he returns to Spain."
Signed from PSG in August 2017, Aurier made his debut for Spurs in a 3-1 win over Borussia Dortmund in the Champions League before going on to make 110 appearances for the club, scoring eight goals.
He has been capped 70 times by the Ivory Coast, whom he captains, and has also netted three times for his country.
Aurier will see some familiar faces when he joins up with his Villarreal teammates.
Former Tottenham players in Juan Foyth and Etienne Capoue are both plying their trade with the Yellows, who sit in 11th in LaLiga.