Chelsea have signed Athletic Bilbao left back Asier del Horno for 12 million euros ($14.50 million) on a three-year contract, the English Premier League champions said on Tuesday.
"Asier is an outstanding international player who will add quality to the squad in a position we needed to strengthen," said Chelsea manager Jose Mourinho in a statement.
"I'm sure he will be a key player as Chelsea continues with its goal to achieve greater success both in England and in the Champions League."
A powerful attacking fullback who is strong in the air, the 24-year-old came through the youth ranks at Athletic.
Del Horno made his debut for Spain last September in a friendly against Scotland and scored the winner against England in a November friendly.
Chelsea have been looking for a player to challenge Wayne Bridge at left back.
Athletic said Del Horno will give a news conference at 1630 GMT on Wednesday with the Spanish club's president Fernando Lamikiz.
He will join up with the Chelsea squad for the start of pre-season training from July 6.
As well as the league title, Chelsea also won the League Cup and reached the Champions League semi-finals last season.
