Swiatek, just 19 and ranked 54 in the world, will take on either Dutch fifth seed Kiki Bertens or Italian qualifier Martina Trevisan for a place in the semi-finals.
"I am surprised I could do this," admitted Swiatek after ending the 17-match winning streak of Halep who was the overwhelming favourite in the absence of 2019 champion Ashleigh Barty and US Open winner Naomi Osaka and the injury-enforced withdrawal of Serena Williams.
"I felt like I played a great match," added Swiatek who will be playing in her first quarter-finals at the majors.
It was a stunning turnaround for the Pole who won just one game against Halep at the same stage in Paris last year, getting swept off court in just 45 minutes.
"Last year I wasn't experienced enough, it was my first match in a big stadium so I was a little stressed.
"But I have made a lot of progress since then, playing girls like Simona, Naomi and Caroline Wozniacki. Now I can handle the pressure."
Swiatek swept through the opening set in just 23 minutes, firing 17 winners to Halep's four.
The teenager tightened her grip, breaking in the first game of the second set with Halep having to fight off four break points in the third game to stay afloat.
Swiatek's assault continued against a player who arrived in Paris with claycourt titles in Prague and Rome.
Halep, 29, saved five more break points in the fifth game but a weary forehand drifted wide and her Polish opponent was 4-1 up with the cushion of a double break.
She took victory on a second match point, ending the tie in 68 minutes on the back of 30 winners and not having allowed Wimbledon champion Halep a single break point.