The season went down to the wire but Green Island ensured there would be no debate when it thumped cellar-dweller Pelichet Bay by nine wickets at Sunnyvale.
University-Grange and Carisbrook-Dunedin did their best, with final-round wins over Albion and Kaikorai respectively, but could not haul in the defending champion.
Green Island took the Bing Harris Trophy with 60 points, ahead of University-Grange (58), Carisbrook-Dunedin (55), Albion (45), North East Valley (37), Taieri (35), Kaikorai (29) and Pelichet Bay (18).
Green Island has dominated Dunedin cricket over the last decade but it was the first time the club had won three successive senior titles.
That had not been done by any club since the 1960s, when first Dunedin and then University won three consecutive titles.
The record is seven straight, achieved by Carisbrook between 1896-97 and 1902-03.
The Swamp Rats had to be patient this season, which looked like it was going to be dominated by the powerful University-Grange squad.
But while Grange won the knockout title and led the Bing Harris for most of the summer, its lead was never insurmountable.
"Plenty of people thought University-Grange had sewn it up a month ago," Green Island stalwart Jeremy Scott said.
"But the lead was never that big.
We had some results go our way and, all of a sudden, we were in front."
The key performers for Green Island over the season were the experienced pair of Dion Lobb and Mark Joyce and former Otago batsman Jordan Sheed.
Lobb had an eight-wicket bag in a clash with University-Grange earlier this month, while both Sheed and Joyce scored more than 800 runs across all forms of cricket this season.
"We weren't getting bowled out and Lobby was cleaning up with the ball.
That was pretty much the key," Scott said.
The wickets were shared on Saturday as Green Island dismissed Pelichet Bay for just 102, with Ian Butler top-scoring for the struggling Bay with 39.
Scott Simpson went early in the reply but Hamish Rutherford (50 not out) and Sheed (38 not out) saw Green Island to victory in the 19th over.
Michael Bracewell scored 70 to lead University-Grange to a 78-run win against Albion at Logan Park.
Sam Wells chipped in with 34 and Ben McCormick had 30 as Grange posted 185 in the 45th over.
The chief destroyer for Albion was left-arm spinner Nick Beard, who continued his fine season with a six-wicket bag.
Albion opener Nathan King then scored 38 but the end came quickly as Mitchell Rutherford grabbed three wickets and three other Grange bowlers took two.
In a straightforward 37-run win against Kaikorai at Bishopscourt, James Hogg top-scored for Carisbrook-Dunedin with 74 and Brad Hamill had the bowling figures of the day, six for 37.
Taieri closed the gap to the top five with a 22-run win against North East Valley.
Ant Harris top-scored with 60, as Taieri reached 143 in 37.3 overs, and Callum Thompson took three wickets to help dismiss North East Valley for 121.
