He and Sam Hain (66no off 32 balls) plundered an eye-watering 170 runs for the third wicket as the Bears wreaked batting carnage and totalled 207 for three from just 16 overs, the match having been reduced after an early rain delay.
Stirling carved the helpless Steelbacks bowlers to all corners, cracking 10 sixes and nine fours, and he hit five sixes in a row from one over from James Sales, who endured a tough T20 debut.
The Steelbacks were never in the hunt in reply as they slumped to 20 for three in the fourth over with key men Chris Lynn and Josh Cobb out cheaply, as well as opener Ben Curran.
Northants continued to try and go for the big hits, but it was a fruitless exercise against a quality attack as the wickets continued to tumble and there was a genuine fear the innings wouldn’t even last not even lasting the 16 overs as they crashed to 55 for seven when Lewis McManus was out in the 10th over.
And that fear was realised as the Steelbacks were eventually dismissed for just 81 with 10 balls of their innings remaining to complete a humiliating defeat.
The Bears had earlier been absolutely relentless and the seemingly powerless Steelbacks attack couldn't simply contain their hosts.
The home side had raced to 60 for two from the six-over powerplay, and although the rains came to offer some respite for Northants, it was only a temporary reprieve.
On the resumption Stirling and Hain just picked up where they had left off, with the bowlers not being helped by a ball made slippery by a wet outfield.
The Bears just slipped through the gears with Stirling bringing up his 50 off just 29 balls and Hain reaching his from only 26.
The pair brought up their 100 partnership in just 49 balls, and just kept going.
Stirling hit the first five balls of the 13th over, bowled by teenager Sales, for six, and missed out on a maximum when the final ball was edged for four, much to the disappointment of the Bears fans in the ground.
That powered the Irishman towards his century though, which came up in the penultimate over as he hit Matt Kelly for four to bring up the three figures in 46 balls.
He was eventually out, caught on the boundary off Ben Sanderson in the final over, but the damage had well and truly been done.
The figures for the Steelbacks bowlers made for grim reading, particularly for debut pair Sales and Kelly, whose five overs combined went for 86 runs.
Scorecard (Match reduced to 16 overs per side): Bears 207-3 (Paul Stirling 119, Sam Hain 66no, Ben Sanderson 2-44) beat Northants Steelbacks 81 all out (Danny Briggs 3-21, Jake Lintott 3-19)