Villarreal want a new left-back after losing Alberto Moreno for six months to a serious ACL injury.
Estupinan will pen a five-year deal at Villarreal and become their fifth signing of the summer.
Villarreal started the La Liga season with a 1-1 home draw against newly-promoted Huesca on Sunday.
Villarreal have now confirmed the signing of Estupinan from Watford on a SEVEN-year contract.
¡El Villarreal ficha al defensa @PervisEstupinan 🇪🇨 para las próximas siete temporadas!
¡Bienvenido al Submarino 👏!
— Villarreal CF (@VillarrealCF) September 16, 2020