Finn Harps defeated Dundalk in a thrilling eircom League promotion/relegation play-off semi-final before a crowd of 3,000 at Finn Park.
The Donegal side will now face Waterford United in a two-legged final next week to determine who plays in the Premier Division next season.
Harps went into this game on the back of a ten-match unbeaten run, including nine wins, and the frustration of being pipped by a point for the Division One title by Cobh Ramblers last weekend.
By contrast, Dundalk's form of late has been mixed, and they finished a full ten points beind Harps in the third spot.
Harps made the breakthrough in the 29th minute. Stephen Parkhouse strode into the penalty area and crossed to the far side where Marc Brolly, unmarked, took the ball down and fired past Chris Bennion.
And Harps could well have added a second on the stroke of half-time when, following a neat exchange of passes, Gethins surged towards the Dundalk goal but Bennion reacted sharply to get down and save.
Dundalk upped their game after the break and Keith Dunne and Paul Marney both had chances as the game really came to life.
Harps were awarded a controversial 74th minute penalty but Conor Gethins' spot-kick was saved by Bennion.
Dundalk were unlucky not to equalise when Robert Doyle crashed a 30-yard effort off the crossbar.
Parkhouse then wrapped it up as he broke through in a one-against-one situation in the final minute.
Dundalk finished with ten men as Doyle got a second yellow card deep in stoppage time.
Finn Harps: Gallagher, McLaughlin, Minnock, Boyle, Holmes, Shields, Funston, McGowan, Parkhouse, Gethins, Brolly.
Sub: Divin for Brolly (86 mins).
Dundalk: Bennion, Flanagan, Grimes, Lynch, Crawley, Perth, K. Dunne, Marney, Doyle, Marney, R. Dunne, McArdle.
Subs: Smyth for Dunne and Mulvenna for McArdle (both 55 mins), Quigley for Perth (65 mins).
Referee: Mr. D. Tomney (Dublin).
