Porto have signed versatile Brazil Under-20 international Danilo from Copa Libertadores champions Santos.
Danilo, who can play on the right side of defence or midfield, made the 13 million euros switch to the Europa League champions on Tuesday.
A statement from the Portuguese club said: "Porto comes to inform that it has reached an agreement with Santos for the acquisition of the sporting rights of athlete Danilo Luiz da Silva. This agreement sees the payment of a fee of 13 million euros."
Porto beat out rivals Benfica, who were also thought to be interested in the young Brazilian's services. Danilo's arrival opens the way for full-back Jorge Fucile to depart the club, with interest coming from the Serie A in the form of Roma and Lazio.