The Croatia international has signed a three-year contract with Diego Simeone's side after spending just one season at San Siro
Atletico Madrid have signed Croatia striker Nikola Kalinic from AC Milan for a fee reported to be in the region of €15 million (£13m/$17m).
Atleti confirmed the arrival of the Croatia striker on their official website, with Kalinic signing a three-year deal with the Liga side.
Kalinic moved to Milan from Fiorentina on a season-long loan with an obligation to buy but his time at San Siro failed to catch fire.
The 30-year-old managed six goals in all appearances for the Rossoneri before leaving Croatia's World Cup campaign under a cloud.
Kalinic refused to come on as a substitute during his country's opening 2-0 win over Nigeria at Russia 2018, citing a back injury, and head coach Zlatko Dalic decided to send him home.
Following Croatia's 4-2 defeat to France in the final, Kalinic elected not to receive a runners-up medal on account of his lack of contribution at the tournament.
Gonzalo Higuain's arrival from Juventus pushed him further down the pecking order at Milan but Diego Simeone's Atletico represent an enticing fresh start for the former Blackburn Rovers forward.
He joins Antoine Griezmann, Diego Costa and fellow new recruit Thomas Lemar among an enviable set of attacking options at the Wanda Metropolitano.
Kalinic, who was also linked with a move to Sevilla, could make his Atleti debut against Inter in the International Champions Cup on Saturday.
Simeone's men face rivals Real Madrid in the UEFA Super Cup in Tallinn next week before opening their LaLiga bid with a trip to Valencia on August 20.