The Premier League club confirmed the deal in a statement on their website on Thursday, with Amat still to undergo a medical before the move can be formally completed.

Amat made his first-team debut for La Liga side aged just 17 before appearing on 26 occasions for them in his first full season as Espanyol secured an eighth-placed finish.

The 21-year-old spent last season on loan at Rayo Vallecano, where he featured 27 times.

Amat becomes manager Michael Laudrup's second signing of the off-season and follows Jose Canas in moving to the League Cup winners.

He is expected to be one of several signings for the Welsh side before the transfer deadline, with Vitesse Arnhem forward Wilfried Bony strongly linked with a move to the Liberty Stadium.

Swansea are looking to add depth to their squad ahead of a UEFA Europa League campaign in the coming season.