Marseille - A drop goal from Anthony Belleau with the last kick of the game gave Toulon a come from behind 18-15 win over 14-man La Rochelle to reach the French Top 14 final on Friday.
Toulon will face either defending champions Racing 92 or Clermont, who meet Saturday, in the final in Paris on June 4.
"We had a good dynamic and prepared well," said Belleau who was only playing after first choice fly-half Francois Trinh-Duc was injured.
"It was hard, but there it is. I thank all the players who helped me and it's thanks to them that we managed to win tonight."
In a tense semi-final played in front of 65,000 people at the Stade Velodrome, the match turned in the 50th minute when La Rochelle, who were leading 15-6 and comfortably placed, were reduced to 14 men.
Centre Pierre Aguillon was red carded for a dangerous tackle on Toulon's James O'Connor which left the Australian star arrowed head first into the turf.
Welsh full-back Leigh Halfpenny, who scored 15 of his team's points in a big-hitting game where neither side managed a try, slotted over three quick penalties to level the semi-final at 15-15.
But a weary La Rochelle, who had finished the regular season on top of the table and were bidding for a first place in the final, had their chances to seal victory in a dramatic final phase.
Zack Holmes, having replaced fellow Australian Brock James, had two shots from the halfway line but his first penalty fell just inches short while the second drifted wide.
Toulon seized their chance and after a series of gruelling forward charges which inched towards the La Rochelle line, 21-year-old Belleau kept his nerve to pop over the winning drop kick after the hooter had sounded.
"Anthony Belleau is a work in progress, but for his age he is very calm and serene," said Toulon scrum-half Sebastien Tillous-Borde.
"We knew that he wouldn't panic, we have a lot of confidence in him."
La Rochelle winger Vincent Rattez said the red card decision was hard to accept.
"It was the turning point. We had to play half an hour with 14 men, but these are the rules. It was cruel but we will try to come back next season."
It was a shattering disappointment for La Rochelle who were only promoted to the top flight three years ago as well as 35-year-old fly-half James who kicked all of his team's points.
However, the win means that the likes of Matt Giteau, Drew Mitchell and Juanne Smith, who all leave at the end of the season, have one more match left to play for Toulon.