In the women's event, Stephens and Keys set up a rematch of the 2017 US Open final
Cecchinato shocks Djokovic to set up French Open semi-final against Thiem
World no 72 Marco Cecchinato stunned former champion Novak Djokovic at the French Open on Tuesday to became the first Italian man in 40 years to reach a grand slam semi-final.
Cecchinato, who had never won a grand slam match in his career before Roland Garros, claimed a 6-3, 7-6, 1-6, 7-6 victory over 12-time major winner Djokovic in front of a packed and raucous Court Suzanne Lenglen crowd.
The 25-year-old Italian goes on to face Dominic Thiem for a place in Sunday's final after the Austrian seventh seed overwhelmed Germany's world No 3 Alexander Zverev in Tuesday's first match on Court Philippe Chatrier.
In an epic fourth set tie-break, Djokovic saved three match points but wasted three set points as Cecchinato became the lowest-ranked man in the French Open semi-finals since 100th-ranked Andrei Medvedev in 1999.
In a roller-coaster of a quarter-final, both men were warned for coaching, 2016 champion Djokovic required two medical timeouts and the Italian was docked a point for unsportsmanlike behaviour.
Djokovic also squandered three set points in the second set and failed to serve out the fourth in the ninth game after being 5-2 in front.
As Cecchinato ventures into uncharted territory, his last-four opponent reached his third successive Roland Garros semi-final in devastating fashion.
Thiem produced a 6-4, 6-2, 6-1 demolition of a hobbled and exhausted Zverev, who admitted he was close to quitting the tie.
German second seed Zverev simply ran out of gas, paying a heavy price for needing three successive five-set matches to reach his first grand slam quarter-final.
His Roland Garros marathon also left him physically drained - he needed his left thigh strapped in the second set.
"He is one of the fittest guys on the tour so it was difficult for him today," said Thiem, the only man to have defeated 10-time French Open champion Rafael Nadal on clay this year.
"I hope we have many more matches at the grand slams but when we are 100 per cent.
"It's great to reach the semi-finals for a third year but it's time to take another step and I will do everything for that."
In the women's event, US Open champion Sloane Stephens brushed aside Russian Daria Kasatkina to set up a repeat of last year's Flushing Meadows final with fellow American and good friend Madison Keys.
The 10th seed produced a clinical performance to down Kasatkina, the conqueror of world No 2 Caroline Wozniacki, 6-3, 6-1 on Court Philippe Chatrier.
Earlier in the day Keys, the 13th seed, reached the semi-finals for the first time by seeing off Kazakhstan's Yulia Putintseva 7-6 (7/5), 6-4.
"I'm excited to play my good friend in the semi-finals, we've already played in the US Open final and it's really good for American tennis," said Stephens.
Keys struck 30 winners past a battling Putintseva in an impressive display, but will have to at least maintain that level in the last four against Stephens.
The 23-year-old struggled last September under the pressure with the US Open title on the line, losing 6-3, 6-0, but she is confident that performance won't affect the match at Roland Garros.
"Honestly, the (US) Open feels like it was 12 years ago at this point," said Keys, who is yet to drop a set in the tournament.
"I obviously rely on what I learned there and how to manage my emotions and manage the moment, but there were so many late nights and I was so tired. It feels completely different here."