Match ends, Watford 0, Bournemouth 4.
Bournemouth boss Eddie Howe says his team "still have room to improve" after they humbled a poor Watford side to move up to fifth in the Premier League.
David Brooks opened the scoring for the Cherries before Joshua King converted from the spot after being brought down by Christian Kabasele, who was sent off for a second bookable offence.
The Norwegian forward then added a third for Bournemouth in first-half injury time, and Callum Wilson wrapped up the win early in the second half.
The victory was Bournemouth's biggest away win in the Premier League.
"It wasn't perfect," Howe told BBC Sport. "I'm pleased but we have room to improve and grow from today. Watford made it difficult, even with 10 [men], but we were professional.
"It's a great start. It is so early it is difficult to make predictions. All we can do is work and try to achieve what our limit is."
Watford looked confident in the early stages, with their best chances falling to Will Hughes, who drew a good save from Asmir Begovic with a shot from the edge of the area.
However, once Kabasele had seen red after 32 minutes, they were never able to find a foothold in the game and Bournemouth played through their lines with ease.
The Cherries had chances to further their advantage in the second half. King fired straight at Ben Foster when crossing may have been the better option, and Ryan Fraser was tackled with King and Wilson in space.
But Eddie Howe's team were unable to add to their four-goal lead, to the relief of the home crowd, who will not remember Vicarage Road's 100th Premier League fixture fondly.
Cherries impress again as strong start continues
Bournemouth's win, their biggest away from home in the Premier League since the 3-0 victory at Chelsea in January, was richly deserved.
They weathered an early storm from Watford and went ahead early through Brooks, who finished off a lightning counter-attack spearheaded by the excellent King.
King was again at the heart of the play for the second goal. He won the penalty, drawing a clumsy foul from Kabasele, before converting the resulting spot-kick.
Wilson has been one of Bournemouth's star performers this season, and his floated cross for King was perfectly weighted, giving the Norwegian a golden opportunity to make it three, which he duly did.
And Wilson, who this week missed out on a first England call-up, got himself on the scoresheet two minutes after the break when he controlled Fraser's cross brilliantly before tapping in.
Howe will also be delighted with how his back four defended, with Nathan Ake the stand-out performer as they kept a clean sheet for the first time in 10 away league games.
Bournemouth have now taken 16 points from their opening eight league games - last season, it took them 16 matches to reach that tally.
With Southampton up next in two weeks, they will hope the forthcoming international break does not halt their momentum.
Watford blown away
Coming into this match, the sides were level on points and could only be separated on goal difference. But there was clear water between them on a wet afternoon in Hertfordshire.
The Hornets had not lost at home to Bournemouth since 1997 and started reasonably well, but Troy Deeney and Andre Gray were unable to capitalise on the half-chances that came their way.
And after they went behind to Brooks' second goal in as many games, Watford offered little.
When Kabasele saw red, Javi Gracia opted to drop Etienne Capoue into central defence alongside Craig Cathcart, a decision that proved costly.
Bournemouth scored two further goals with Capoue at centre-back, and captain Deeney was visibly annoyed at the Frenchman after Wilson's goal.
Maybe it was Deeney's displeasure that prompted Gracia to bring on Adrian Mariappa, a recognised centre-back, in the 55th minute. But by then, it was too late.
After winning their first four league games of the season, the Hornets have now gone four without victory and are ninth in the table.
The international break has perhaps come at a good time for Gracia and his team, who have two weeks to prepare for their trip to in-form Wolves, where they will look to rediscover their early season sharpness.
Man of the match - Nathan Ake (Bournemouth)
'We're capable of beating anyone' - what they said
Bournemouth manager Eddie Howe, speaking to Sky Sports: "We are very pleased with the result. This is a tough place to come and Watford have been in good form.
"We believe we are capable of beating anyone when we are on top of our game. We like to stay in the background and as underdogs. We will go about our work in a controlled way."
Watford manager Javi Gracia, speaking to BBC Sport: "It is always a bad moment to lose like today. Today is the first day we haven't competed as in other games. They were much better than us. We will try to improve for the next game."
Ill-disciplined Watford - the best of the stats
- Since returning to the Premier League in 2015-16, Watford have been shown more red cards than any other side in the competition (13).
- Bournemouth are just the second side to beat Watford by four or more goals in the Premier League at Vicarage Road, after Man City (0-5 in May 2017 and 0-6 in September 2017).
- Watford have conceded 19 penalties in the Premier League since the start of the 2015-16 season. Only West Ham (22) have given away more.
- Bournemouth scored four goals away from home in a Premier League game for only the second time, and the first since August 2015 (4-3 at West Ham).
- Bournemouth's Joshua King has scored 34 goals in the Premier League - only four Norwegians have scored more (Ole Gunnar Solskjaer, Steffen Iversen, John Carew and Tore Andre Flo).
- Bournemouth's David Brooks has scored in successive league games for the first time in his career.
After the international break, Watford travel to Molineux to face Wolves on Saturday 20 October, and Bournemouth host Southampton on the same day. Both games kick off at 15:00 BST.
- 15CathcartBooked at 22mins
- 27KabaseleBooked at 32mins
- 25HolebasBooked at 68mins
- 16DoucouréBooked at 89mins
- 19HughesSubstituted forMariappaat 55'minutes
- 37PereyraSubstituted forDeulofeuat 74'minutes
- 18GraySubstituted forSuccessat 55'minutes
- 3S Cook
- 15A Smith
- 20BrooksSubstituted forGoslingat 70'minutes
- 16L CookSubstituted forSurmanat 78'minutesBooked at 87mins
- 24FraserSubstituted forStanislasat 66'minutes
- Jonathan Moss
- Shots on Target
Second Half ends, Watford 0, Bournemouth 4.
Corner, Watford. Conceded by Andrew Surman.
Delay over. They are ready to continue.
Delay in match Adam Smith (Bournemouth) because of an injury.
Abdoulaye Doucouré (Watford) is shown the yellow card for a bad foul.
Jefferson Lerma (Bournemouth) wins a free kick in the defensive half.
Foul by Abdoulaye Doucouré (Watford).
Adam Smith (Bournemouth) wins a free kick in the defensive half.
Foul by Gerard Deulofeu (Watford).
Andrew Surman (Bournemouth) is shown the yellow card for a bad foul.
Foul by Andrew Surman (Bournemouth).
Kiko Femenía (Watford) wins a free kick on the right wing.
Foul by Simon Francis (Bournemouth).
Gerard Deulofeu (Watford) wins a free kick in the defensive half.
Corner, Bournemouth. Conceded by Adrian Mariappa.
Attempt missed. Junior Stanislas (Bournemouth) right footed shot from outside the box is high and wide to the right. Assisted by Andrew Surman following a corner.
Corner, Bournemouth. Conceded by Craig Cathcart.
Offside, Watford. Abdoulaye Doucouré tries a through ball, but Troy Deeney is caught offside.
Attempt saved. Joshua King (Bournemouth) right footed shot from the right side of the box is saved in the bottom right corner. Assisted by Simon Francis.