Sol Bamba will leave Middlesbrough after his one-year contract expired.
The 37-year-old returned to football with Boro after he recovered from non-Hodgkin lymphoma in May last year.
The Ivory Coast defender played 29 times for the club but he will now leave Chris Wilder's side.
Wales international Neil Taylor and fellow defender Lee Peltier also go, but captain Jonny Howson is to be offered a new deal.
Howson, 34, missed just one league game all season and the midfielder was named the club's player of the year.
The news comes two days after Boro missed out on a spot in the Championship play-offs, following a 4-1 loss at Preston North End as they finished seventh.