Krejcikova, ranked 33 in the world and playing just her fifth main draw in a Slams singles event, triumphed 6-1, 2-6, 6-4 for a second career title.
The 25-year-old emulates compatriot Hana Mandlikova who claimed the trophy in Paris in 1981.
As it happened: Pavlyuchenkova vs Krejcikova
The 25-year-old Krejcikova dedicated her victory to her mentor, the former Wimbledon champion Jana Novotna who died of cancer at the age of 49 in 2017.
“It’s hard to put into words. I cannot believe I have just won a Grand Slam,” said Krejcikova who was still outside the top 100 when the 2020 French Open took place last October.
“I spent a lot of time with Jana before she died. Her last words to me were ‘enjoy tennis and try and win a Grand Slam’.
First Kiss 😘#RolandGarros | @BKrejcikova https://t.co/lYBFblTWtZ
— Roland-Garros (@rolandgarros) 1623511915000
“I know she’s looking after me. All this is pretty much because she is looking after me.
“It was amazing that I got the chance to meet her. She was such an inspiration. I miss her and I hope she’s really happy.”
In a nervy start to the final, Krejcikova was broken in the first game, serving up two double faults.
Respect 🥰@BKrejcikova + @NastiaPav #RolandGarros https://t.co/jQ9zYozwxv
— Roland-Garros (@rolandgarros) 1623512838000
However, the 29-year-old Russian was unable to capitalise and dropped the next six games as her Czech opponent grabbed three breaks and raced way with the opener inside half an hour.
Krejcikova was rewarded for her bold attacking, hitting 13 winners to the Russian’s seven.
Pavlyuchenkova, who made her Slam debut back in 2007, was the more composed player in the second set, stretching out to 5-1.
A medical timeout at 5-2, during which she was seen munching Haribo gummy bears, merely delayed the Russian levelling the final.
In the decider, the players exchanged breaks in the third and fourth games, before the Czech broke to love for 4-3 on the back of a 10-shot rally.
Pavlyuchenkova saved two championship points in the ninth game and a third in the 10th but Krejcikova became champion on the fourth when the Russian hit long.
Both women capitalised on a draw in which the top seeds fell and just kept falling.
World number one and 2019 champion Ashleigh Barty hobbled out in the second round.
Serena Williams was knocked out in the fourth round, world number two Naomi Osaka withdrew after one match, while 2018 champion Simona Halep never even made it to Paris.