The 28-year-old Schwartzman triumphed 7-6 (7/1), 5-7, 6-7 (6/8), 7-6 (7/5), 6-2 and will face either 12-time champion Rafael Nadal or Italian teenager Jannik Sinner for a place in the final.

It was one marathon too many for Thiem, the runner-up in Paris for the last two years, who had needed five sets and three and a half hours to down world number 239 Hugo Gaston in the fourth round.

The 5ft 7in (1.70m) Schwartzman's success came on the same day that compatriot Nadia Podoroska, the world 131, reached the last-four of the women's singles.

"Dominic is one of the great players. He is my best friend and I have a lot of respect for him," said Schwartzman.

"So this win is very important for me. In the second and third sets, I was going a little crazy and I was screaming at myself because I had so many chances.

"But, come on, I deserved to win tonight," added Schwartzman who defeated Nadal in the Rome quarter-finals on the eve of the French Open.

Thiem had been attempting to reach a fifth successive semi-final in Paris.

However, despite crunching 65 winners to his opponent's 47, he committed 81 unforced errors in a match which featured 19 breaks of serve and at five hours and eight minutes was the second longest of the tournament.

"I was over the limit today," said Thiem.

"At the net I just told him that he deserves it. I think he's for the first time top 10 with that win. 
"That's also great achievement."

Schwartzman recovered from a break down in the 65-minute first set to sweep through the tiebreaker.
But Thiem kept hammering away forcing the Argentine to save seven break points in the ninth game of the second.

The Austrian broke through for a 6-5 edge before wrapping up a 71-minute set.

In a tie of dramatically fluctuating rallies, eight breaks of serve punctuated the third set.

Schwartzman even had a set point but couldn't convert and Thiem pounced in the breaker to sneak ahead.

The Argentine blinked again in the 10th game of the fourth as three more set points went begging, but he clung on, snatching the breaker after a 73-minute set.

By this stage, they had been on court for over four and a half hours.

However, a wear Thiem was broken in the sixth and final game of the decider as Schwartzman celebrated becoming the 10th Argentinian man to make the semi-finals of a major.