Northampton (14) 24
Tries: Reihana, Ashton, Lamont Cons: Reihana 2, Myler Pen: Reihana
Wasps (11) 20
Try: Waldouck Pens: Walder 5
New Saints signing Neil Best tries to escape James Haskell's clutches
Promoted Northampton handed struggling champions Wasps their third straight defeat of the new Premiership season.
Saints took the lead through Bruce Reihana's converted try but Wasps hit back through a Dominic Waldouck try and two Dave Walder penalties.
Walder's third after Chris Ashton's converted try for Saints made it 14-14.
A penalty apiece kept the sides locked together and although Walder once again put Wasps back in front, Sean Lamont's converted try gave Saints victory.
Despite missing four penalties Northampton full-back Reihana bagged 17 points in total in front of an ecstatic sell-out Franklin's Gardens crowd, but it was a day to forget for his opposite number Josh Lewsey.
The England international's mistakes led to both Northampton's first-half tries.
Despite the contribution of Reihana, the game was won in the pack where the outstanding Ignacio Fernandez Lobbe out-muscled the Wasps forwards.
Saints took the lead inside the first minute as Reihana charged down Lewsey's kick before scoring and adding the conversion.
Walder got Wasps on the board with a penalty before quick passing from a line-out ended with Waldouck going over in the far corner to make it 8-7 to the visitors.
Walder extended Wasps' lead with his second penalty and although Reihana missed one for Northampton, they re-took the lead when Lewsey dropped Carlos Spencer's kick.
Former Wigan rugby league player Ashton, who grabbed 39 tries in National League One, ran in under the posts for his first Premiership try.
Reihana converted but missed two penalties and Walder levelled the scores at 14-14 on the stroke of half-time.
A penalty apiece from the two kickers made it 17-17 and both sides were reduced to 14 men on 48 minutes when Rob Webber and Dylan Hartley were sent to the sin-bin for using their knees on each other in the tackle.
In an electric atmosphere, both Reihana and Walder missed a penalty apiece before the Wasps fly-half landed one from just inside his own half to make it 20-17.
The champions briefly looked set to claim their first league win of the campaign but four minutes later Saints conjured up the winning score.
Replacement Stephen Myler's long cut-out pass to left wing Lamont enabled him to score out wide and Myler converted as Wasps' early season woes continued.
Northampton boss Jim Mallinder:
"It's satisfying to win - you've got to look at yourselves and look at your performances.
"It wasn't the complete performance but I think we did enough to get a win.
"It's a physical battle against Wasps. You've got to beat them physically and you've got to compete with them and come out on top in that area.
"We went three points down at one stage but we didn't force things, we came back and scored that great try from Sean Lamont which was really encouraging."
Wasps director of rugby Ian McGeechan:
"Obviously it was one we wanted to win and we came here with that intention.
"Probably with our execution in the second half we were trying to play a bit too much rugby - it's disappointing for us but we'll just keep our heads down and keep working.
"Last week (against Worcester) I was annoyed because it was unacceptable to lose that game when we had won it.
"Today we didn't get ourselves into a strong enough position in the second half. Some of our decision making at the moment isn't as astute as it should be."
Northampton: Reihana; Ashton, Ansbro, Downey, Lamont; Spencer, Dickson; Tonga'uiha, Hartley, Murray, Fernandez Lobbe, Day, Best, S Gray, Wilson.
Replacements: Myler for Downey (62), Foden for Dickson (59), Smith for Tonga'uiha (62), Stewart for Murray (62), Rae for Fernandez Lobbe (62).
Not Used: Shields, Hopley.
Sin Bin: Hartley (47).
Wasps: Lewsey; Sackey, Waldouck, Flutey, Voyce; Walder, Reddan; Payne, Ward, Vickery, Birkett, Palmer, Worsley, Haskell, Hart.
Replacements: Robinson for Reddan (62), Barnard for Payne (40), Webber for Ward (37), Leo for Birkett (64), Betsen Tchoua for Haskell (67).
Not Used: Staunton, Hoadley.
Sin Bin: Webber (47).
Ref: Chris White (RFU).