The Spaniard has been sacked following a run of poor results that leaves Middlesbrough second bottom of the Premier League table.
The Teesside club have yet to win a game in 2017 and have decided to part ways with the former Real Madrid man – just three days before their game with Manchester United.
Karanka steered the side to promotion last season but was unable to produce consistent results in Englands’s top division – winning only 4 games so far this season.
In a statement released by the club Karanka said: ‘This club will always hold a special place for me and I wish everyone connected with Middlesbrough Football Club the very best for the future.”
Middlesbrough face Manchester United on Sunday in dire need of three points to keep their survival chances alive.