Brisbane Heat 160 for 7 (Renshaw 90*) beat Melbourne Stars 159 for 7 (Larkin 58, Neser 4-25) by three wickets
Chasing 160 for victory, the visitors stuttered and surged several times before reaching their target in a dramatic finish at the MCG on Monday night.
Renshaw was the matchwinner, top-scoring with an unbeaten 90 from 56 deliveries.
But Heat still needed four off the last ball and Renshaw delivered, scooping Webster's final delivery over the in-field to the rope.
Renshaw was given a lifeline on 47 when he was dropped by Clint Hinchliffe, who misjudged the flight of the ball in the deep.
Stars also failed to run out Renshaw on 63 when Adam Zampa couldn't gather Nathan Coulter-Nile's throw with the batter well short of his ground after a mix-up with Jimmy Peirson.
The 83-run partnership between Renshaw and Peirson (22 from 18) was vital before the former steered his side home with the tailenders. Renshaw's innings included six fours and four sixes.
But Larkin took 14 runs from the first four balls of Neser's final over - the last of the innings - before the Test quick finally got his revenge by dismissing the Stars batter.
Webster (36 off 34) and Tom Rogers (26 off 23) did some damage for the Stars, as did James Seymour (13 off 6), whose brief innings included two sixes.
Neser claimed the wickets of Webster and Coulter-Nile in consecutive deliveries during the 16th over but missed out on what would have been his second hat-trick of the season.
Stars were without high-profile allrounder Marcus Stoinis for a fourth consecutive match because of a hamstring injury. He was named in the extended squad but was not included in the final team after pulling up sore following a fitness test.