Ben Duckett hit a majestic 84 and Alex Wakely a crucial 53 as Northants recovered from 15 for three to post 161 for eight.
That proved to be too many for a Notts side packed full of international players, as they responded with 153 for nine, the Steelbacks bowling proving too good.
Chron snapper Kirsty Edmonds was at the game to capture the best of the action, and here are a selection of her brilliant pictures.
Northants will now play the winner of the second semi-final between Yorkshire and Durham in Saturday night’s final.
Report and reaction from that game will also be at northamptonchron.co.uk after the match.