Lynn, who belted an unbeaten 115 against Warwickshire at Edgbaston last month, maintained his superb T20 form this season, clubbing seven sixes and 10 fours in a career-best 117 off 56 balls at Sophia Gardens, Cardiff on Wednesday (Thursday AEST).
The 36-year-old white-ball specialist from Queensland, who has plied his devastating trade with the bat in the Big Bash League and all across the globe, was caught by Asa Tribe off Jimmy Neesham in the 17th over as Northants made 7-217 before restricting Glamorgan to 164 all out in reply.
The veteran Aussie opener, who has cemented his reputation as one of the most destructive T20 batsmen in the world, recorded the highest individual score by a Steelbacks batter and helped secure a home quarter-final berth with two games to spare.
A ninth win from 10 Blast matches this season has left them 12 points clear at top of the Central and West Group.
Elsewhere, Jason Roy bludgeoned an unbeaten 58-ball 103 as Surrey boosted their hopes of making Finals Day with a comfortable eight-wicket win against South Group's bottom side Sussex at The Oval.
Chris Jordan and Tom Lawes took two wickets apiece to help reduce Sussex to 7-176 before Roy, who hit eight sixes and six fours, steered Surrey home two down with 16 balls to spare.
South Group leaders Hampshire saw their lead cut at the top after slipping to a five-wicket defeat to Middlesex.
Durham skipper Alex Lees continued his fine form this season as his 44-ball 80, including four sixes, helped them cruise to an eight-wicket win against Leicestershire.
Brydon Carse, England's leading wicket-taker in the Ashes series earlier this year, marked his first appearance of the season after recovering from a hand injury by taking 1-17 off his four overs for Durham.
Somerset kept their faint hopes of progressing alive thanks to opener Will Smeed's 51-ball 89 in a 27-run win over Derbyshire.
With AAP.
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