Mourinho, 58, was dismissed after only 17 months in charge, even though he could have led the club to their first silverware since 2008.
Tottenham have been struggling in their bid to qualify for the Champions League via a top-four finish in the Premier League.
Spurs are currently seventh, five points behind fourth placed West Ham, and suffered a shock Europa League last-16 exit against Dinamo Zagreb.
"The club can today announce that Jose Mourinho and his coaching staff have been relieved of their duties," a Tottenham statement said.
The bombshell news came less than 24 hours after Tottenham announced they were one of 12 clubs planning to launch a breakaway European Super League.
Tottenham's academy coach Ryan Mason, a former player at the club, will take first-team training this week and is set to pick the team for tomorrow's Premier League clash with Southampton and the League Cup final at Wembley.