The central defender has signed a four-year deal with the Capital One Cup winners, subject to a medical and international clearance.
|9/4||Swansea are 9/4 with William Hill to finish in the top half next season
The Spaniard becomes the Swans' second signing of the summer, following Jose Canas' free transfer from Real Betis.
Michael Laudrup's continues to seek further bolstering of his squad, with a second loan-long deal spell for Villarreal midfielder Jonathan de Guzman looking close to completion.
However, club captain Ashley Williams is edging closer to a summer exit after agreeing terms with Arsenal.