Novak Djokovic reached his ninth Roland Garros semi-final on Thursday, sweeping past Alexander Zverev to keep his bid to become just the second man to hold all four Slams at the same time twice firmly on track.
Thiem reached the semi-finals for a fourth successive year with a 6-2, 6-4, 6-2 victory against Russian 10th seed Karen Khachanov.
The last time Djokovic made the semi-finals was 2016 when he went on to win the title. He has a 6-2 career lead over Thiem and beat the Austrian in the Rome semi-finals in the run-up to Paris.
However, Thiem came out on top in the Roland Garros quarter-finals in straight sets in 2017.
Fifth seed Zverev, bidding to reach a maiden Slam semi-final and become the first German in the last-four in Paris since Michael Stich in 1996, made the stronger start.
But top seed Djokovic levelled immediately before claiming the set on a Zverev double fault.
Djokovic dominated the second set as breaks in the second and eighth games were enough to tighten his grip. The world number one saved two more break points in the opening game of the third set and again made the German pay with a break for 4-2. Zverev's 40th and last unforced error proved to be the final point of the one-sided quarter-final.
Thiem was utterly dominant on Court Suzanne Lenglen, hammering 29 winners, as his erratic opponent contrived to tally 37 unforced errors and only 17 winners.
Khachanov had impressed in a fourth-round victory over Juan Martin del Potro, but was never in with a chance in the quarter-final, which was delayed from Wednesday due to rain, dropping serve twice in the opening set.
He managed to get to 4-4 in the second, only to see Thiem reel off eight of the next 10 games and seal a last-four spot without even facing a break point in the match.
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