— Liverpool FC (@LFC) August 16, 2014
The 22-year-old becomes the eighth summer signing, who will wear No.18 shirt for the Reds this season.
However – the fee for Moreno were not disclosed but it has been reported that the fee could be around somewhere in the region of £12 million.
The full back has scored three goals in 43 games last season as the club won the Europa League and finished fifth in La Liga.
The Spaniard, who has three caps for his nation – will be available to play for the Merseysiders from next weekend.