Tsitsipas won 6-3, 6-3, 4-6, 4-6, 6-3 and will face either Nadal or Djokovic in the championship match Sunday
Stefanos Tsitsipas became the first Greek player to reach a Grand Slam final Friday when he defeated Germany's Alexander Zverev in a bruising five-setter at the French Open.
Fifth-seeded Tsitsipas won 6-3, 6-3, 4-6, 4-6, 6-3 and will face either 13-time champion Rafael Nadal or world No 1 Novak Djokovic in the championship match.
However, the 22-year-old will have his work cut out Sunday - he is 2-7 against Nadal and 2-5 playing Djokovic.
Tsitsipas was in tears after making his first final at the majors, secured on a fifth match point.
Tsitsipas took a 5-2 career lead over Zverev into the semi-final and he was the first to pounce with the only break of the opening set in the second game.
The rock-solid Greek didn't give up a single break point although in an indication of the fine margins, Tsitsipas only hit one winner.
Zverev, bidding to become the first German man since Michael Stich in 1996 to reach the final in Paris, raced into a 3-0 lead in the second set.
However, Tsitsipas' greater composure saw him rack up six consecutive games to move two sets ahead.
The Greek had come into the semi-final certainly sharper having seen off three seeded players to get this far.
Zverev had needed five sets to beat his 152nd-ranked compatriot Oscar Otte in the first round and hadn't faced a player inside the top 45 before Friday.
But Zverev carved a break in the third game of the third set and this time backed it up despite a lengthy, foul-mouthed rant at the umpire over a disputed line call.
The 24-year old German, now fired up, broke in the opening game of the fourth set and levelled the semi-final in the 10th game on the back of a brutal 27-shot rally.
Tsitsipas, playing in his third consecutive semi-final at the majors, crucially saved three break points in the first game of the decider.
He made the most of the escape, breaking the German for 3-1 and quickly securing the advantage for 4-1.
In a 10-minute eighth game, Zverev saved four match points, the second of which with a drop shot, the third with an ace.
However, Tsitsipas held his nerve and claimed victory after over three and a half hours on court with his eighth ace of the match.