Northampton suffered their first home league defeat since October 2023 to Gloucester, who claimed revenge for a 14-try mauling in May.
Santiago Carreras scored two tries and kicked 10 points as Gloucester made up for their humiliating 90-0 defeat at Franklin's Gardens at the end of last season.
Northampton's director of rugby Phil Dowson said: "It's hugely disappointing. We were poor in the first half and credit to Gloucester because they were excellent, they got right on top of us and we gave ourselves too much to do in that second half.
"Emotionally we weren't in the right place and Gloucester came here all guns blazing and had a point to prove.
"They proved it, we didn't stand up for the fight and that's probably the most disappointing thing."
One positive for Northampton was England scrum-half Alex Mitchell making his first appearance of the season after recovering from a neck injury.
But they lost England fly-half Fin Smith to a head injury assessment early on while George Hendy was also forced off.
"Alex Mitchell's input was excellent", Dowson added.
"For him to be away for that long and to come back and play so well and have such an impact was great.
"Fin Smith passed his head injury assessment but he couldn't see out of one of his eyes because he got a knee to the eye.
"George Hendy failed his head injury assessment."
Gloucester head coach George Skivington was delighted with his side's display, but victory did not make up for their mauling in May.
"I will never forget that match but I'm not sure winning cancels it out," Skivington said.
"Santi (Carreras) was outstanding. He showed his world-class pedigree in this game, scoring tries, slotting kicks and it's really good to see him back doing that.
"It was just one of those days where our big names turned up for us, everyone grafted and I'm delighted with the attitude."
Exeter suffered a seventh successive Gallagher Premiership defeat of the season as Bath regained top spot with a 19-15 victory at the Recreation Ground.
It was not a game that will live long in the memory, but Bath had enough to thwart Exeter and leave them stuck at the Premiership basement.
Flanker Guy Pepper, No 8 Miles Reid and replacement hooker Niall Annett scored tries for Bath, with fly-half Finn Russell adding two conversions, although a vastly-improved performance will be required in their next game against Investec Champions Cup opponents La Rochelle.
Exeter often belied their league position as Jacques Vermuelen crossed for a try and Henry Slade kicked a penalty, remaining in the contest until Annett's score 13 minutes from time finished them off, although No 8 Greg Fisilau's 80th-minute effort that Slade converted secured a losing bonus.
Chiefs remain the only side in this season's Premiership without a league win, and they are already a distant 18 points adrift of the play-off places.
Bath, though, have no such worries, nudging West Country rivals Bristol into second place without remotely hitting top gear.
In Sunday's only fixture, Arron Reed scored twice as Sale recorded a thumping 39-25 bonus-point win over rivals Leicester at Salford Stadium.
Sale went behind in the 11th minute when prop Nicky Smith ploughed his way over the line from close range. Fly-half Handre Pollard skewed his conversion attempt well wide but he kicked a penalty in the 19th minute to extend Leicester's lead.
Sale barely escaped their own half during the opening quarter but Dan du Preez touched down in the right corner in the 23rd minute.
Moments later Pollard kicked his second penalty to put Leicester 11-5 up, but in the 31st minute, the hosts scored their second try when Bevan Rodd went over from close range after good work from a line-out. Du Preez then converted to put Sale 12-11 ahead at the break before they extended their lead two minutes into the second half.
A superb break inside the left channel saw the hosts cut Leicester apart before Reed finished off in the corner. Five minutes later, Reed scampered over again for his second and Asher Opoku-Fordjour then collected possession and charged under the posts for Sale's fifth try.
Leicester hit back through Freddie Steward's well-taken try down the right flank, which Pollard converted, after Joe Heyes had been sin-binned for an illegal challenge on Hyron Andrews.
But Sale scored again through the impressive Luke Cowan-Dickie and Du Preez converted, giving him a nine-point haul with the boot in total.
