The 23-year-old has signed a four-year contract with Sevilla.
The Spain Under-21 said: “I’m very happy because Sevilla is the team where I want to be, for the fans, for the team, for the city, everything, for it’s a pleasure to be at Sevilla.”
Sanchez added on SFC Radio: “The chance to play in the Champions League with Sevilla is a real prize.
“The squad did very well last season and were rewarded with third place. I’ve come here with lots of hope and motivation and I’m ready to help the club achieve the aims they have set.
“This team aspires to win everything.”