DONE DEAL: Lamine Kone signs new five-year deal at Sunderland AFC
The deal will see the 27-year-old Ivory Coast international remain on Wearside until 2021.
Manager David Moyes said: "Lamine is an important player for this club and I made that clear to him from the outset."
The 27-year-old arrived in January from French side Lorient, signing a four-and-a-half-year deal.
Kone has now agreed a new and improved contract to remain with the Black Cats until 2021.
The Black Cats managed to hold on to star defender Kone this summer despite fierce interest from Premier League rivals Everton.
The Toffees made a bid of Â£18million for Kone earlier in the summer transfer window, but Sunderland were determined not to lose one of their best players.
Deadline day passed without any further bids from Everton and contract talks took place this week.
Everton lodged an Â£18m offer in early August, which then led to a statement being put out in Kone’s name claiming he wanted a move after Sunderland had failed to offer him a promised new deal – a claim rejected by the club.
Sunderland confirmed they would be offering him a new deal once the window had closed but decided to offer Kone a new contract earlier, ahead of the recent Middlesbrough game.
Kone then complained of a bad back less than 24 hours after turning down the offer, which saw him miss the defeat to Boro and an EFL Cup win over Shrewsbury Town.
Kone returned to the first team for the 1-1 draw with Southampton and started the 3-0 defeat to Everton on Monday night.