The Northern Ireland rider was locked in battle with Peter Hickman in the shortened two-lap race, but Dunlop led all the way and had the upper hand on the final lap on his MD Racing Yamaha, closing out another win around the Mountain Course by 3.2s for his ninth Supersport victory, one more than Ian Hutchinson.
Both Dunlop and Hickman (Trooper Beer Triumph) were on lap record pace on the last lap, but strong winds on the Isle of Man and particularly on the Mountain section prevented any improvement on Dunlop’s new 129.475mph benchmark, which he set in the opening Supersport race on Monday.
It was also a 52nd victory for the Dunlop racing dynasty, with Michael now only two wins behind John McGuinness, who is the second most successful TT rider ever, while Joey Dunlop still holds the all-time record with 26 triumphs.
Hickman won the Superbike, Superstock and Supertwin races, but any prospects of a five-timer to equal Hutchinson's historic 2010 feat were thwarted by Dunlop, although the English ace is the hot favourite for the blue riband Milwaukee Senior TT (2.15pm) as he targets a fourth win of the festival.
Dean Harrison finished third on the DAO Racing Kawasaki, 21.3s behind Hickman, with Davy Todd on the Milenco by Padgett’s Racing Honda in fourth.
Todd was 17.5s back on Harrison and 6.4s ahead of Jamie Coward (KTS/Steadplan Yamaha), with Ramsey’s Conor Cummins completing the top six (Milenco by Padgett’s Racing Honda).
James Hillier (OMG Yamaha) and Dominic Herbertson (Cowton Kawasaki) were the top eight.
Cork’s Mike Browne sealed an excellent ninth on the Burrows Engineering/RK Racing Yamaha ahead of Magherafelt man Paul Jordan on the PreZ Racing Yamaha.
Lee Johnston was a retirement following the first lap after struggling with eye problems.