Both sides needed to win the crucial match at Kingsholm to stand any chance of finishing sixth in the Premiership and, with it, land a lucrative Heineken Cup spot for next term.
But two tries from Sale full-back Rob Miller - along with 14 points from the boot of fly-half Nick Macleod - was enough for them to see off Gloucester, whose points came through a try from wing Charlie Sharples and four penalties and a conversion from number 10 Freddie Burns.
As if the European qualification was not enough of an incentive for both teams, the match took on extra significance after Gloucester head coach Bryan Redpath surprisingly resigned in midweek.
He is rumoured to be heading to Sale but Kingsholm director Ryan Walkinshaw has threatened a "no holds barred legal attack" if he discovers the Cheshire club "manufactured" a move for the former Scotland scrum-half.
And the tension of the match spilled over within minutes of kick-off as home wing James Simpson-Daniel was bumped into touch metres from the Sale line, prompting a mass brawl to break out on the touchline.
That ended with Gloucester flanker Akapusi Qera and Miller getting 10 minutes in the sin-bin.
The lively start did not end there as both Burns and Macleod got their accounts off the mark with a penalty each, and both sides looked to run the ball across their backs.
And, within the space of a minute, both teams scored converted tries.
Sale were first as centre Will Addison flipped a neat pass to full-back Miller to cut inside and go over near the posts.
Straight from the restart, Sharks lock Andrei Ostrikov dropped the ball on his left and allowed Sharples to snaffle possession and race over.
It was turning into a real heavyweight, all-or-nothing clash between two sides desperate to play on Europe's big stage next season - and neither would give an inch in the opening half.
But Gloucester went into the interval with a six-point lead as Burns landed two more penalties in the closing minutes of the half.
The hosts looked to be in the driving seat when Burns popped over his third penalty in 14 minutes to put them nine points clear but a deft slight of hand from England wing Mark Cueto saw Miller dash through a midfield gap and race over for his second touchdown.
Suddenly the boot was on the other foot as Sale pressed further. Ex-England prop Andy Sheridan was a powerhouse in the loose and, when home prop Dan Murphy dropped a scrum, Macleod booted his second penalty to bring his side back to within a point.
Sale were certainly the better side as Gloucester found it difficult to get out of their own half at times, let alone score more points.
And, when Macleod was handed the chance to boot for goal with the wind at his back from the halfway line, he made no mistake and put his side back in front at a crucial time.
Macleod dropped a goal from 15 metres with five minutes left, which left Gloucester needing a converted try to win.
They had one last chance when a move in the Sale half came to lock Alex Brown but the former England second row dropped the pass and the Sharks celebrated their vital victory.
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