Bristol City have signed defender Tomas Kalas from Chelsea for an undisclosed fee, which is a club record for the Championship club.
The 26-year-old Czech Republic international spent last season on loan with the Robins, featuring 41 times in all competitions.
Kalas was on the books at Chelsea for nine years, but only made four first-team appearances for the Blues.
The centre-back has agreed a four-year contract with the Ashton Gate side.
"We saw last season the qualities he brings and Tomas is exactly the type of player we want to build our team around," head coach Lee Johnson told the club website.
"Not only is he a fantastic footballer but someone with a winning mentality."
All four of Kalas' outings for Chelsea came under Jose Mourinho in the 2013-14 season.
He had loan spells with Sigma Olomouc, Vitesse Arnhem, Cologne, Middlesbrough and Fulham before his switch to Bristol City last summer.
Find all the latest football transfers on our dedicated page.