Victory also secured Biarritz a place in next season's Heineken Cup and the 36-year-old believes it provided the perfect leaving present after 15 years at the top of the game.
"It's huge for me," said Marconnet, who won 84 caps for France, with his first international appearance coming way back in 1998.
"Even in my wildest dreams I didn't think about finishing my career in that way.
"It's such a happy time for me and it's a happy end to the season for Biarritz.
"A few months ago the club was struggling against relegation from the Top 14 but now we've won a title. I'm really touched.
"It's a huge pleasure to end my time with a trophy. It's unbelievable to finish a career like that."
A difficult domestic campaign saw Biarritz start as second favourites against a star-studded Toulon team on Friday yet they controlled large parts of the game and were good value for their narrow win.
And while Marconnet will understandably be handed plenty of praise for his incredible achievements now that his boots have been hung up for good, the man himself insists it was the selfless manner of everyone involved with the club that saw Biarritz come good when it really mattered.
"It's a great reward for en extraordinary squad," added Marconnet, whose career ended with 88 European appearances, 76 of which came in the Heineken Cup.
"Biarritz Olympique are still a big European team and it's fantastic that they will be playing in the Heineken Cup again next year. I believe the club deserve to be in that position.
"We remained united even in difficult times this season. Our win wasn't thanks to our rugby - it was thanks to our spirit.
"Even when Biarritz Olympique was in a tough position, everybody stayed united behind the club. This is a reward for the entire city."