The 20-year-old French Open champion from Latvia rallied from a set down to beat the debutante finalist 6-7 (5), 6-1, 6-4, in a match that lasted two hours and 15 minutes.
“I’m really happy to win my second title here and in my career,” Ostapenko said after the match. “I enjoyed playing here and to also see so many Latvian flags is amazing.”
Sunday’s win was Ostapenko’s first hardcourt title since her upset victory over third-seed Simona Halep at the French Open in June.
Despite her defeat, Haddad Maia said competing in her first Women’s Tennis Association finals had been a good experience.
“This match today was really tight. Both of us were playing very well,” she said.
Ostapenko, the first Latvian to win a Grand Slam tournament, was a huge crowd favourite in Seoul throughout the week-long tournament.
The final match drew around 9,000 spectators, Yonhap news agency said, the tournament’s first sellout since it began in 2004.
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