Worcestershire skipper Daryl Mitchell and Joe Clarke put together a superb double century stand as their side rewrote the record books and reached a 401 target in 80 overs with six balls to spare against Northamptonshire at New Road.
Joe Leach sealed a memorable win with a six off Ben Sanderson to seal a two wicket win.
It was Worcestershire's highest ever success run chase at their headquarters and the second biggest in their history.
Victory kept alive their hopes of promotion ahead of next week's vital clash with leaders Essex at Chelmsford.
Mitchell completed his second 100 of the game and in the process went past 10,000 first class runs in his career.
Clarke's fifth ton of the campaign in first class cricket took him past 1,000 runs in a campaign for the first time in what is his first full season.
They added a total of 232 in 47 overs for the third wicket after joining forces at 36-2 in the 10th over.
Mitchell reached the 10,000 milestone when on 23 via a single off Northants paceman Ben Sanderson at an average of 39.21 with 23 centuries and 42 fifties.
The two captains, Mitchell and Alex Wakely, came to an agreement to set up a game on the final day after the home side had resumed on 193-3 in their first innings.
Worcestershire declared 350 runs behind after adding eight runs to secure a bonus point to leave Mitchell unbeaten on 107.
Northants then scored 50 for the loss of Ben Duckett, caught by Mitchell at third slip off Jack Shantry, before pulling out in their second innings.
That left Worcestershire needing to score at five an over to secure their fourth Championship win of the campaign.
Opener Brett D'Oliveira was dismissed for a single, edging Rory Kleinveldt through to keeper David Murphy.
Tom Fell looked in good touch and scored four boundaries in racing to 22 but then shouldered arms to Kleinveldt and was bowled.
Worcestershire reached 48-2 off 15 overs by lunch with Mitchell unbeaten on 15 and Joe Clarke 13.
The third wicket pair looked in good touch after the interval and their 50 stand came up in 14 overs and the 100 in the 26th over.
Clarke went to his half century with his eighth boundary when he hammered a full toss from Rob Keogh through mid wicket. It came off 82 deliveries.
Mitchell reached his fifty when he clipped Rob Keogh to the square leg boundary – from 95 balls with six boundaries.
At tea Worcestershire stood on 199-2 from 45 overs with Mitchell on 68 and Clarke 96.
Clarke's three figures came up from 129 balls with 16 boundaries and Mitchell's second hundred of the game was achieved from 160 deliveries with nine fours.
The pair lifted the total to 268-2 in the 57th over when three wickets fell to Ben Sanderson in the space of five balls.
Mitchell (103) was caught at backward point, George Rhodes (5) fell at mid wicket and Clarke (125) was trapped lbw to leave Worcestershire on 275-5.
Ross Whiteley came in and took the attack to the Northants bowlers, lofting Sanderson for successives sixes over long on and square leg and then pulling Steven Crook over the ropes.
A fourth six from the left-hander – over mid wicket off Chad Barrett – took the Worcestershire total past 350.
But the game again swung back into the melting pot with two wickets in two overs.
Whiteley, having made 45 off 30 balls, was yorked by Chad Barrett after adding 78 in nine overs with Ben Cox.
Then Ben Cox's fluent knock of 34 off 30 deliveries ended when he chipped Keogh to mid on.
Joe Leach struck three fours in an over from Barrett and then Ed Barnard (8) edged Sanderson and was caught behind at 391-8.
Jack Shantry played out a maiden from Kleinveldt to leave 10 required from the final two overs.
But the left hander hit Sanderson for a straight four and then Leach punched the air in delight after smashing the winning six off the last ball of the 79th over
