Lisburn captured the Fred Daly Trophy when Jack Shellard scrambled a par to win the decisive point at the 19th at Tramore Golf Club.
The final was poised at two points apiece during a titanic battle with Connacht champions Galway and all eyes turned to match five where the destination of the title was on the line.
Fittingly for such a closely contested decider, it required an extra hole to find a winner. Shellard had to produce heroics on 18 just to keep the contest alive. Trailing Harry Colbert, Lisburn's anchor-man eagled the closing par five to square the match.
The two remaining combatants returned to the first in a bid to settle their encounter. Although Shellard missed the green and left his pitch four paces from the hole, he drained the 12-footer, which rocked Galway and ultimately proved decisive when Colbert missed his putt for par.
Aaron Marshall (1 hole) and Josh Black (4&3) also won points for the Ulster side but wins for Liam Nolan (2&1) and Sean Nohilly (5&4) meant that the final hinged on the bottom match.
In the Irish Junior Foursomes, Munster winners Mitchelstown will meet Co Sligo and Leinster champions Waterford face Warrenpoint in Sunday morning's semi-finals.
The final is scheduled for a 1pm start. Meanwhile, the inaugural Junior Inter-Club All-Ireland is down for decision from 9am.
Fred Daly Trophy, Tramore Golf Club
Lisburn 3 Galway 2 (Lisburn names first)
Aaron Marshall beat Luke O'Neill 1H; Joshua Robinson lost to Liam Nolan 2&1; Josh Black beat Gavan Keogh 4&3; Kyle Patton lost to Sean Nohilly 5&4; Jack Shellard beat Harry Colbert 19th
Lisburn 4 Dungarvan 1 (Lisburn names first)
Aaron Marshall beat Daniel Raher 5&4; Joshua Robinson beat Jake O'Riordan 3&1; Josh Black beat Michael Troy 4&3; Kyle Patton lost to Barry Morrissey Jnr 5&4; Jack Shellard beat Ethan Raher 6&5
Greystones 1 Galway 4 (Greystones names first)
Niall Gaffney lost to Luke O'Neill 3&1; Ben Hynes lost to Liam Nolan 4&2; Rory Reid lost to Gavan Keogh 6&4; Christopher Lawless halved with Sean Nohilly; Robbie O'Brien halved with Harry Colbert.
Irish Junior Foursomes, Tramore Golf Club
Sunday 30 September
Mitchelstown v Co Sligo (Mitchelstown names first)
0800 Sean Leonard (2) & Tristan Nolan (12) v Aoghdan Brady (6) & Daniel Ford (2) - Mitchelstown receive 3 shots;
0808 Tommy Maher (12) & Adam Luddy (6) v Tom Flanagan (2) & Niall McDermott (4) - Mitchelstown receive 6 shots
Waterford v Warrenpoint (Waterford names first)
0816 Rory Lehan (10) & Ed Fitzpatrick (12) v Bailey Wilson (5) & Jack Murtagh (7) - Waterford receive 5 shots;
0824 Alex Byrne (9) & Jack Keane (7) v Rian Carvill (2) & Dylan Medlicott (9) - Waterford receive 3 shots.
Final provisionally scheduled for 1300
Irish Boys Inter-Club, Tramore Golf Club
Sunday 30 September
18 holes of stableford
0900 Caolan Smith (Tullamore), James O'Callaghan (Ballybunion)
0908 Liam Delaney (Tullamore), Edmond Healy (Ballybunion)
0916 Callum Bergin (Tullamore), Sean Malone (Ballybunion)
0924 Ciaran Farrell (Tullamore), Lochlann McHale (Ballybunion)
0932 Daniel Fox (Tullamore), Ewan McHale (Ballybunion)
0940 Mark Hunter (Carrickfergus), Rory Donnellan (Tuam)
0948 Taylor Morrison (Carrickfergus), Ciaran McGrath (Tuam)
0956, Josh Millar (Carrickfergus), Adam Carton (Tuam)
1004 Marcus Baird (Carrickfergus), Oisín Roche (Tuam)
1012 Jamie Arthur (Carrickfergus), Eanna Costello (Tuam).