St Thomas' (Galway) 0-18 Ruairi Og, Cushendall (Antrim) 2-11
Defender David Sherry was the toast of St Thomas' after popping up with a remarkable winning point five minutes into stoppage time at Parnell Park.
The corner-back was released to play as a sweeper due to Cushendall's five-man attack and took on the responsibility to stride forward for the winner at the death.
The sides had been level after a terrific fight-back from Cushendall who'd trailed by eight points late in the first-half and by seven at half-time.
But Sherry was calm in the eye of the storm and after being fed by Bernard Burke struck a brilliant score from a tight angle out on the left wing.
Ulster champions Cushendall did their best to level the game for the third time late on but simply couldn't conjure another score.
It means St Thomas' progress to the March 17 final at nearby Croke Park though they will feel they have plenty of improving to do after this display.
They bounced back from an early Cushendall goal from a penalty by Neil McManus to dominate the first-half and led 0-13 to 1-3 at the break.
Kevin Lally's side had six different scores in that period including the excellent Eanna Burke who clipped 0-3 for the south-Galway outfit.
Cushendall, in turn, clung on to McManus' goal and scored just a point from play in the first-half, by Sean McAfee.
But everything changed in the third quarter as Cushendall took advantage of the wind at their back to come roaring back into the contest.
They outscored St Thomas' by seven points in the first 20 minutes of the second-half with Fergus McCambridge scoring 1-1 during that blitzkrieg.
Substitute Conor Carson fed McCambridge for the goal with a wonderful flick and then set up Paddy McGill for a point with another clever flicked pass.
Cushendall were level twice late on and it remained deadlocked in the fifth minute of stoppage time but Sherry provided that sweet moment to save St Thomas' blushes and secure their place in the decider.
Scorers for St Thomas': N McManus 1-6 (1-0pen, 0-4f, 0-2 65), F McCambridge 1-1, P McGill 0-2, S McAfee, E Campbell 0-1.
Scorers for Ruairi Og, Cushendall: Darragh Burke 0-6 (0-4f), E Burke 0-3, B Burke, J Regan 0-2, D Sherry, S Cooney (0-1f), C Cooney, K Burke, D McGlynn 0-1.
St Thomas': G Murray; D Sherry, C Burke, C Mahoney; D Cooney, S Cooney, F Burke; J Regan, David Burke; C Cooney, Darragh Burke, B Burke; E Burke, B Farrell (S Skehill 58), K Burke (D McGlynn 33).
Subs: D McGlynn for K Burke 33, S Skehill for Farell 58.
Ruairi Og, Cushendall: E Gillan; S Delargy (S Walsh 54), M Burke, D Kearney; E Campbell, A Graffin, P Burke; F McCambridge, N McManus; R McCambridge (C Carson h/t), E McKillop, D McNaughton; P McGill, S McAfee, A Delargy.
Subs: C Carson for R McCambridge h/t, S Walsh for S Delargy 54.
Ref: P O'Dwyer (Carlow).