Mario Pasalic has joined Atalanta from Chelsea on a permanent deal after the Serie A club exercised an option in the terms of his loan.
The 25-year-old midfielder moved to Gian Piero Gasperini's side on a season-long loan in July 2018 and that deal was extended for another campaign last year.
Atalanta have reportedly paid €15million to sign the Croatia international on a permanent basis.
Pasalic joined Chelsea from Hajduk Split in 2014 but did not make a senior appearance for the Blues in six years.
He was loaned to Elche, Monaco, Milan and Spartak Moscow before joining Atalanta, where he has enjoyed the best football of his career.
"We thank Mario for his service to the club and wish him the best of luck for the next chapter of his career," Chelsea said in a statement.
Pasalic has scored seven goals in 33 appearances in all competitions in 2019-20, helping Atalanta challenge for the top four in Serie A and reach the quarter-finals of the Champions League.