The Polish world No. 1 was upset by the 26-year-old Czech player 7-5, 6-7, 3-6 in the championship match, failing to claim her 11th career singles title and ending her 10-match winning streak.
After the match, Świątek congratulated Krejčíková on her performance and pledged to donate her Ostrava prize money to Polish nonprofit organizations ahead of World Mental Health Day on Monday.
The Polish star has picked up 60 wins and seven titles this year.
Last month, she won the US Open, capturing her third Grand Slam trophy.
The 21-year-old, coached by countryman Tomasz Wiktorowski, in early April took over as the new number one in women's tennis, becoming the first Pole to top the world rankings.
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Source: Canal+, PAP