Rakitic, 26, had caught the eye of Europe’s top clubs after starring during Sevilla’s run to the Europa League trophy.
He arrives at Barca after the club announced last week Cesc Fabregas was leaving to join Chelsea and he is seen as a natural replacement for the Spain playmaker.
Rakitic, who was born in Switzerland, is a "multi-faceted midfielder who combines two great virtues: physical strength and technical quality," Barca said in a statement on their website.
After coming through the youth ranks at Basel, Rakitic joined Bundesliga side Schalke 04, where he spent four seasons before moving to Sevilla in 2011.
As club captain and the team's dominant personality, he helped the Andalusian club win last season's Europa League and is representing Croatia at the World Cup finals in Brazil, where he put on a fine performance in the opening match of the tournament against the hosts in Sao Paulo.
As part of the Rakitic deal, Barca and Sevilla agreed that Barca B team player Denis Suarez would be loaned to Sevilla for the next two seasons.
- Sports & Recreation
- Europa League
- Cesc Fabregas