The winger signs as an immediate replacement following the departure of Scott Sinclair to Manchester City, adding to his Spanish compatriots Michu and Chico at the Swans
The versatile winger can play in any attacking midfield role and joins the Swans as an immediate replacement for Scott Sinclair, who left for Manchester City for a fee of up to £8 million.
The 27-year-old made 45 appearances in all competitions for Los Che last season, scoring 5 goals, and has won four Spain international caps.
Commenting on his move he told Sky Sports News: "I am happy. It's my dream to play in the Premier League."
He joins Jonathan de Guzman and compatriots Michu and Chico as manager Michael Laudrup's summer signings from La Liga, and is also joined in midfield by South Korea international Ki Sung-Yueng who completed his move from Celtic last week.
The Danish international legend has had to reshape the Welsh side since replacing Brendan Rodgers, following the departures of key players Steven Caulker, Joe Allen, and Gylfi Sigurdsson, but has so far both their opening Premier League matches scoring 8 goals and conceding none.