The Toon boss has parted company with the club only three league games into the new season.
It is unclear whether if Keegan was sacked or if he walked out on the Magpies.
Dennis Wise, the club's executive director of football, is the hot favourite to take over with the bookies.
Keegan, 57, took charge of Newcastle for a second time in January after Sam Allardyce was axed.
He has endured a difficult transfer window, with the sale of James Milner to Aston Villa for £12million a low point.
Argentina pair Fabricio Coloccini and Jonas Gutierrez did arrive but the signings have been far from inspiring.
Keegan's first spell at St James' Park began in 1992 before resigning five years later.
KEVIN KEEGAN'S second reign at Newcastle ended today after less than eight months
The Toon boss has parted company with the club only three league games into the new season.
It is unclear whether if Keegan was sacked or if he walked out on the Magpies.
Dennis Wise, the club's executive director of football, is the hot favourite to take over with the bookies.
Keegan, 57, took charge of Newcastle for a second time in January after Sam Allardyce was axed.
He has endured a difficult transfer window, with the sale of James Milner to Aston Villa for £12million a low point.
Argentina pair Fabricio Coloccini and Jonas Gutierrez did arrive but the signings have been far from inspiring.
Keegan's first spell at St James' Park began in 1992 before resigning five years later.