Söderling, a two-time French Open finalist, had to save three match points at 5-6 down in the third set, with Llodra notably netting a forehand when the Swede was at the net and the court was at his mercy.
Llodra had never previously gone beyond the third round at a Masters event but he fought back from 5-2 down in the decisive tie-break, as a roller-coaster of an encounter reached crescendo after two hours and 49 minutes.
“My God, tennis is frustrating!” said 30-year-old Llodra, who is a member of the France team set to take on Serbia in the Davis Cup final on December 3rd-5th.
“But there you go, I have nothing to reproach myself for. I tried, I gave everything, I wasn’t far away and even though I’m disappointed, there’s still a great opportunity in the Davis Cup final.”
Despite the pain of defeat, the left-hander could console himself with the satisfaction of having produced arguably the best tennis of his career.
Having already beaten world number three Novak Djokovic and world number 11 Nikolay Davydenko en route to the semi-finals, he thrilled the Bercy crowd with his throwback style on Saturday.
His game at the net was particularly impressive and some spectacular volleys enabled him to whitewash Söderling in the first-set tie-break, before the Swede drew level after securing the decisive break in the second set.
Llodra required treatment on blisters in the decider but still had the strength to hit back from 4-2 down to force the tie-break.
Söderling’s victory sends the 26-year-old into the first Masters final of his career and, after final defeats at Roland Garros in 2009 and 2010, he will hope for better luck on the other side of the city.
“I hope that this will be the one,” said Söderling, who declared himself “happy and definitely lucky to have got through”.
Later on Saturday Söderling learned that Gael Monfils is to be his opponent in ATP Paris Masters final, after the French 12th seed stunned top seed Roger Federer 7-6 (9/7), 6-7 (1/7), 7-6 (7/4).
Monfils fought back from 4-1 down in the third set to reach the final at the Bercy arena for the second year in succession, following his defeat by Novak Djokovic last year.
Monfils had lost all five of his previous meetings with world number two Federer, but he took a well contested first set when the Swiss superstar netted a forehand at 7-8 down in the tie-break.
The second set was every bit as tight as the first, but Federer managed to level the match after sweeping his way imperiously through the tie-break.
The game appeared up for Monfils in the third set as he fell 4-1 down, but the world number 14, roared on by a typically boisterous Bercy crowd, dug deep to see off five match points and scrap his way into the final
“I went to the limits of myself,” said a jubilant and exhausted Monfils.
“I feel better and better as the tournament goes on. I ran out of juice a little bit at the start of the third set but the fans were there, they pushed me and I kept believing.”
Federer, who is still to reach a Paris Masters final, was guilty of several uncharacteristic errors when the match appeared his for the taking and must now steel himself for an assault on the year-end ATP World Tour Finals in London.
“There were two pretty extraordinary matches today,” said Federer.
“We could have had a Llodra-Federer final and it turned into a Monfils-Söderling final. What’s disappointing is that I was in control of the situation with a break up in the third set.”
“Of course it hurts. On one of the match points I had the whole court open and I couldn’t put it in, a bit like Llodra in his match.”