Marketa Vondrousova, a 17-year-old qualifier, beat Anett Kontaveit in the final of the Biel Bienne Open to win the title in only her second WTA event.
The Czech world number 233 edged Estonia's 99th-ranked Kontaveit - who beat Britain's Heather Watson in the first round - 6-4 7-6 (8-6).
Vondrousova had beaten Czech compatriot and world number 18 Barbora Strycova in the semi-final in Switzerland.
Sunday's victory moves her close to the top 100 for the first time.
"It's the biggest win of my career, because I'd mostly played smaller tournaments," Vondrousova told the WTA.
"This was one of my first big tournaments, and I was injured in my left elbow for a lot of last year. I had to do a lot of fitness, which helped me become a better mover.
"Now I'm playing really great."
In Marrakech, Croatia's Borna Coric saved five match points to defeat Germany's Philipp Kohlschreiber 5-7 7-6 (7-3) 7-5 and clinch his first ATP title at the Grand Prix Hassan II.
Coric, the 20-year-old world number 79, trailed 3-0 in the second set and 4-2 in the decider before he rallied to beat the third-seeded Kohlschreiber, who was bidding for an eighth title.