Her win over Svitolina - which included a 21-minute service game at 4-3 in the opening set - is her second over a top-10 player, having ousted world No.5 Sofia Kenin in Rome last month.
"I'm super happy that I can't really believe it," said Krejcikova during her on-court chat with Fabrice Santoro.
"I'm so happy that I was able to play my tennis, that my game plan was working. I think most of my shots have been actually amazing. I think it was so far, I think my best match. I'm just really happy that I'm here, that I'm enjoying the game, that I'm entertaining the crowd, thank you so much for coming today. I'm just extremely happy."
Djokovic aces third-round test, and French interview
World No.1 Novak Djokovic faced no trouble during his 6-1, 6-4, 6-1 third-round victory over Lithuanian Ricardas Berankis and did his best to get through a lengthy post-match interview in French with Cedric Pioline.
The Serbian 18-time Grand Slam champion, is a wizard with languages, and is fluent in his native tongue, English, Italian and can get by in French as well.
Djokovic is through the Roland-Garros fourth round for a 12th consecutive year, and has taken sole ownership of the Open Era record for the longest streak of last-16 appearances on Parisian clay. He next faces Lorenzo Musetti.