Having won the title so impressively last season, Chelsea now find themselves just one point above the relegation zone having lost nine of their 16 Premier League games - including their last two against Bournemouth and Leicester.
And Roman Abramovich's patience has now run out, with Mourinho getting the boot before the weekend's clash with fellow strugglers Sunderland.
After Monday's 2-1 defeat at Premier League leaders Leicester, Mourinho insisted he wanted to remain in charge, but hit out at Chelsea players he felt had "betrayed" him with their performance.
"One of my best qualities is that I can read the game and identify the strengths of the opponent and tell my players what they are. So it is a big frustration to accept the goals because my work was betrayed, if that is the right word," he said.
"I worked four days on this match. I prepared everything related to the opponent. I identified four movements where they scored almost all their goals.
"My players got all that information, you can ask them, they are honest guys who will tell you it is true. But in the situations I identify, we concede the first and second goal. The mistakes were there."
In October, Chelsea issued a statement of the club's "full support" behind Mourinho, but accepted "results have not been good enough and the team's performances must improve", but this campaign has developed into the London club's worst start to a season since 1978, at the end of which they were relegated.