Green Island beat defending champions Southern 45-34, while Dunedin overcame University 22-15 in their respective semifinals this afternoon.
Green Island, who finished the regular season at the top of the table, shattered Southern's hopes of a three-peat at Bathgate Park.
But it was an even encounter for the first half, with both teams trading tries before Southern took a 19-14 lead at halftime.
After Southern scored an early penalty, Green Island were aggressive and piled on points.
Southern hit back to narrow the gap, but Highlander Oliver Haig and newly signed Highlander Finn Hurley - who also scored 15 points with the boot - scored late to seal the victory.
At Kettle Park, University got on the board first through captain Aaron Withy's try, but Dunedin took the lead through two penalties from Cameron Burgess.
Dunedin led 11-10 at halftime and surged ahead to win.
