Athletic Bilbao have wrapped up a deal which will see Mikel San Jose join on a permanent basis from Liverpool.
The youngster spent the 2009/10 campaign on loan with the Primera Liga club, greatly impressing during his time at San Mames.
He has signed a contract which will keep him with the Basque outfit until June 2015, with the agreement also including a €30million buy-out clause.
The commanding defender learnt his trade in the academy ranks at Bilbao before being snapped up by Liverpool for £270,000 in 2007.
Three years at Anfield followed but he failed to make a senior appearance for the Reds.
Having struggled to make the grade he was shipped back to Spain last summer in a deal which gave Athletic the option to sign him should they wish to do so.
He made 25 appearances for Joaquin Caparros' team during the 2009/10 season, helping them to an eighth-place finish.