Harlequins clung on to a losing bonus point against Northampton to claim the final European Champions Cup spot in a frantic and thrilling final game of the season.
The two teams finished level on 52 points but one more win for the team from London sees them return to the big time after three years out of the European limelight.
Saints' victory secured seventh place and they will now be hoping Gloucester lose the European Challenge Cup final so they can go into a play-off for another chance of qualifying for the Champions Cup.
In a thrilling contest at Franklin's Gardens Northampton threw everything at Quins in the second half, taking the lead while the visitors were down to 14 men through Api Ratuniyarawa's try with 10 minutes to go, but John Kingston's men held out.
Harlequins had the perfect start thanks to a bad kick from Nafi Tuitavake, who kicked out on the full when Saints went back into their 22 at the kick-off.
It gave Quins a lineout in Saints' 22 and after a clever chip from Karl Dickson put them on the home team's tryline, James Horwill was driven over.
Nick Evans converted to give Quins a 7-0 lead after just three minutes.
Evans extended the lead on nine minutes with a penalty, but the home side replied with a try from George North on 14 minutes thanks to a brilliant tap inside from Harry Mallinder, who was back at No. 10 thanks to injuries to Stephen Myler and JJ Hanrahan.
Mallinder converted to make it 10-7, though Saints had to contend with skipper Tom Wood going off injured inside the first quarter.
Evans missed a chance to add three more points and Saints took advantage.
A superb kick from Nick Groom forced Marland Yarde to fumble into touch, giving Northampton a five-metre lineout.
A throw to the back saw Louis Picamoles wrap around and offload to Alex Waller to dive over, Mallinder adding the extras to put the home side 14-10 in front after 25 minutes.
Evans missed a second very gettable penalty but in a helter-skelter 40 minutes Joe Marchant restored Quins' lead, picking up from five metres out after a break from Mike Brown was stopped only by a brilliant tackle from Jamie Gibson.
Evans found his radar to make it 17-14 but Mallinder made it 17-17 at the break to leave it as you were with 40 minutes to go.
Mallinder missed a drop-goal attempt and Evans instead nudged Quins three points ahead 10 minutes into the second half before going off with a shoulder injury.
A 40-metre break from North should have resulted in a Northampton try but the home side spilled the ball over the line.
On 59 minutes the television match official intervened to see Charlie Matthews sin-binned for a deliberate knock-on in his 22 and Northampton looked to have taken immediate advantage with a try from Tuitavake, but it was scrubbed off because of a forward pass from Luther Burrell.
Joe Marler was lucky not to get another yellow for lying on the ball as Saints desperately piled on the pressure, but they held out a second time.
Tim Swiel looked to have zipped through to score in a rare Quins attack, but was downed by an ankle tap by Ahsee Tuala despite the full-back slipping to the floor.
It looked as though Quins were going to survive the sin-bin but Horwill's high tackle on Ben Foden gave Saints another five-metre lineout and the pressure eventually told with Ratuniyarawa squirming over.
Mallinder hit the post with the conversion from right in front and the home side could not find the further points they needed to grab sixth.