The visitors scored on the break in the 51st minute after midfielder Tiemoue Bakayoko lost the ball and Callum Wilson played a neat one-two with Jordan Ibe before slotting home.
Wilson was also involved in the second goal, when he pushed the ball to Junior Stanislas who flicked it into the net off sprawling goalkeeper Thibaut Courtois in the 65th minute.
Former Chelsea midfielder Nathan Ake made it three barely three minutes later, prodding the ball in from a Stanislas shot.
Chelsea’s first home defeat since Sept. 30 exposed the London side’s lack of firepower, with Alvaro Morata injured, Michy Batshuayi on his way to Dortmund on loan and Olivier Giroud signed from Arsenal only a few hours before kickoff.
Bournemouth boss Eddie Howe expressed joy at the performance of his team, adding that it was the best result the club has ever achieved.
The result matched Chelsea’s defeat at Roma in the Champions League on 31 October, and was also the joint-heaviest defeat of Conte’s two-and-a-half-year spell in charge of the Blues.
“That has to be our best result and the best performance in getting the result,” he said.
“We were very aggressive and everyone was magnificent. Our aggressiveness, work-rate and endeavour – it all came together. Although it was a game of few chances, we deserved the victory and scored some great goals.”.
In another match, Tottenham Hotspur solidified their top- four credentials with a dominant 2-0 win over Manchester United in front of an English Premier League record crowd at Wembley on Wednesday.
Christian Eriksen gave the hosts the lead after 11 seconds, the second fastest goal in Premier League history.
Manchester United’s woeful defending was exposed again for Tottenham’s second, with Phil Jones turning the ball into his own net after 27 minutes.
The win lifted Tottenham two points behind third-placed Liverpool and Chelsea in fourth as second-placed Manchester United dropped 15 points behind leaders Manchester City.
Tottenham manager Mauricio Pochettino, speaking after the match, praised his players for putting up a fantastic performance.
He added that the result had put his team in a good position for a top four finish.
“It’s a fantastic dressing room after a fantastic performance. The performance was great and I congratulate the players because they deserve all the credit.
“The first goal was a fantastic goal. Christian Eriksen believed that it would arrive in this situation. We tell the young players to always anticipate.
“I am so pleased we are in the race for the top four.
“There’s a lot of games to play and that is why we need to stay focused.
“The early goal for us was good so that we can go on and dominate the game. That goal gave us more confidence and belief.
“Dele Alli was very good today, but all the team was great. The quality of performance was fantastic.
“It’ll be tough against Liverpool now because they are one of the best teams — but it’s about taking it one game at a time.”
Manchester United manager Jose Mourinho, on his part, said the goals scored against his side were ridiculous.
“It’s a performance that starts with a ridiculous goal. That goal after a few seconds has a big influence in the game because Tottenham can play the way they like to play.
“In the end, we played against a very good team. Both goals were ridiculous goals.
“The first goal is an accumulation of mistakes in spite of the fact that everything happened so fast. My players have watched the Tottenham kick-off many, many times.
“It was a really, really bad goal. After the first goal the team had a good reaction — we were there and tried to create.
“The second goal mentally kills the team. A team to win matches needs to score goals and also defend well — on this occasion we were very bad.’’
Also, Theo Walcott scored twice in his second appearance for Everton as they beat Leicester City 2-1 at home on Wednesday to move further clear of English Premier League relegation danger.
Walcott, who joined Everton from Arsenal for about 20 million pounds in the current transfer window, converted Gylfi Sigurdsson’s low cross from close range after 26 minutes.
He then volleyed home before half-time to double the lead.
Jamie Vardy reduced the arrears from the penalty kick spot deep into the second half.
This was after the referee spotted a Wayne Rooney foul on Wilfred Ndidi, to set up a nervy finale for the hosts in which Leicester’s Kelechi Iheanacho twice hit the woodwork.
Everton, who flirted with relegation danger earlier in the season, are ninth in the table while Leicester are three points above Sam Allardyce’s side in seventh.