Declan Devine's team ran away with the victory in the semi-final replay to clinch a spot in the final at the Aviva Stadium, where they will face Liam Buckley's Saints
After playing out a 1-1 draw at the Brandywell, the Candystripes triumphed by a score of 3-0 over Alan Mathews' side to book their place in the final at the Aviva Stadium.
Stephen McLaughlin granted Declan Devine's team a 1-0 lead before half time when he got on the end of a Simon Madden cross.
McLaughlin then doubled Derry's lead midway through the second half when he dribbled past the Shelbourne defence and struck past Chris Bennion.
The rout was completed when Barry Molloy fed David McDaid through with a precise pass and the striker made no mistake in compounding Shels' misery to make the final score 3-0.
Derry City will face St Patrick's Athletic in the final of the competition at the Aviva Stadium on Sunday, November 4. The two sides previously met in the final in 2006, with Derry emerging victorious on that occasion.