Stellini lasted four matches after replacing Antonio Conte last month.
Sunday's heavy defeat to the Magpies placed Tottenham's top four prospects in jeopardy, with the North Londoners now residing in fifth position, six points adrift the top four.
Ryan Mason has been placed in interim charge until a permanent replacement is found.
'Sunday's performance against Newcastle was wholly unacceptable,' Spurs chairman Daniel Levy wrote in a statement on Monday night.
'It was devastating to see. We can look at many reasons why it happened and whilst myself, the board, the coaches and players must all take collective responsibility, ultimately the responsibility is mine.
'Cristian will leave his current role along with his coaching staff.
'Cristian stepped in at a difficult point in our season and I want to thank him for the professional manner in which he and his coaching staff have conducted themselves during such a challenging time. We wish him and his staff well.'
'Ryan Mason will take over head coach duties with immediate effect. Ryan knows the club and the players well. We shall update further on his coaching staff in due course,' Levy's statement continued.
'I met with the player committee today - the squad is determined to pull together to ensure the strongest possible finish to the season.
'We are all clear we need to deliver performances which earn your amazing support.'
