Alexandre Letellier's 89th-minute penalty save helped Angers into the Coupe de France final before Karl Toko Ekambi capped a dramatic conclusion in its 2-0 win over Guingamp.
For much of a turgid affair at Stade Raymond Kopa, Thomas Mangani's well-taken goal shortly before half-time looked to have settled this semi-final.
But in a remarkable finish, Guingamp - Coupe de France winner in 2009 and 2014 - was awarded a spot-kick when Angers captain Cheikh Ndoye was adjudged to have handled a cross when the ball struck him squarely in the stomach.
Justice was done, however, as visiting skipper Jimmy Briand saw his penalty tipped onto the left-hand post by Letellier, before substitute Ekambi rifled home in stoppage time as Angers booked their place in the final of this competition for the first time in 60 years.
On that occasion they were beaten by Toulouse and few would back them to lift the trophy for the first time next month with Ligue 1's joint-leaders Monaco and Paris Saint-Germain to contest Wednesday's second semi-final.
With Guingamp safely ensconced in mid-table and Angers not in realistic danger of relegation from the top flight, this encounter provided both with the opportunity to add some glamour and intrigue to the end of their respective campaigns.
But perhaps overawed by the occasion, both teams struggled for fluency in the final third, the tone set in a scrappy opening half an hour that saw little by the way of goalmouth action.
Alexandre Mendy and Briand did go close for Guingamp, before Angers suddenly sparked into life and forged ahead in the 38th minute.
Jonathan Bamba broke forward down the right and his pass was dummied by Famara Diedhiou into the path of Mangani, who kept his composure to rifle home despite the best efforts of defender Etienne Didot on the line.
The lead was almost doubled in the final minute of the half, but Guingamp goalkeeper Karl-Johan Johnsson raced from his line and denied Kevin Berigaud's volley with a sprawling block.
Angers began the second period as brightly as they had ended the half, Ndoye heading narrowly wide, but the game soon descended back into the pattern seen for much of the first half.
That was until the dramatic finale, Letellier brilliantly denying Briand from the spot before Ekambi shot low past Johnsson to book Angers' date with either Monaco or PSG at Stade de France.