Briton Emma Raducanu became the first qualifier to reach the US Open final by beating Greece's Maria Sakkari 6-1, 6-4.
Sakkari leveraged her powerful serve and excellent court coverage to overpower Pliskova and dedicated her win to the people of Greece, who have endured a summer of brutal wildfires.
Sakkari dictated most of the points and was greatly helped by her opponent's unforced errors.
Third seed Serena Williams advanced after a gritty, tension-filled 6-3, 6-7(6), 6-3 win over Greece's Maria Sakkari.
The Greek rallied from a set down to beat the 23-time Grand Slam champion 5-7, 7-6(5) 6-1 and reach the quarterfinals.