Elena Rybakina's superb run in the United States was ended by Petra Kvitova, who won 7-6 (16-14) 6-2 to clinch the Miami Open title.
Two-time grand slam champion Kvitova, 33, became the second-oldest Miami champion, denying young gun Rybakina a Sunshine Double in the process.
Rybakina, fresh from her triumph at the Indian Wells Open, has been in stunning form but could not find her groove on Saturday.
After clinching the first set following a marathon tie-break, Kvitova took momentum into the second, cruising into a 5-2 lead before sealing the win with a break – Rybakina sending a forehand long.
Kvitova equalled Simona Halep as the players with the third-most WTA 1000 titles (nine), with only Serena Williams (13) and Victoria Azarenka (10) having won more since 2009.
"It feels unbelievable. I'm 33, and it's my 30th title, so I'm very happy," Kvitova told Amazon Prime Sport.
"I didn't think, that was the key. Elena didn't lose a tie-break [this season]. I thought, well, she has to lose at some time. I had to be a bit more aggressive, it was a bit of a struggle. I was a bit nervous, yes.
"I would have laughed [if someone told me I was going to win] but it feels great for sure. Nobody expected this, not me, not my team. I'm happy I'm injury free and, oh my God, I made it."
Kvitova is the second woman to win the singles title in Miami after turning 33, following Serena Williams in 2015.
Indeed, only Serena Williams (68), Justine Henin (42), Venus Williams (40), Kim Clijsters (40) and Maria Sharapova (36) have more WTA singles title to their name in the 21st century than the Czech.
Rybakina, meanwhile, will lament the chance of a Sunshine Double going begging.
The 23-year-old is the fourth player to fail to win the Sunshine Double in Miami's final after Serena Williams (1999), Lindsay Davenport (2000) and Sharapova (2006 and 2013).
"I want to congratulate Petra for a great two weeks here in Miami, and good luck for the rest of the year," said Rybakina. "Thank you to my team, we'll keep going."