Sunderland secured their Premier League status with a 3-0 victory over Everton on Wednesday, relegating Newcastle and Norwich in the process.
The two sides join already relegated Aston Villa to the championship next season ahead of the last match next weekend.
Newcastle managing director Lee Charnley has apologised to the club's fans after the Magpies were relegated from the Barclays Premier League for the second time in seven years.
Derby rivals Sunderland's home victory over Everton consigned their neighbours to the Sky Bet Championship once again along with Norwich and Aston Villa, casting doubt on the future of manager Rafael Benitez, who has a release clause in the contract he signed in March.
In a statement directed at the club's fans, Charnley said: "Tonight we are devastated at our relegation from the Premier League, as I know every single person connected to this football club will be."