Fifth seed Ons Jabeur, who finished runner-up at Wimbledon, booked a spot in the US Open quarter-finals for the first time with a 7-6(1) 6-3 victory over Veronika Kudermetova of Russia.
Jabeur will meet Australia's Ajla Tomljanovic for a place in the semi-finals.
TOMLJANOVIC MOVES PAST SAMSONOVA
Australia's Ajla Tomljanovic followed up her third-round victory over Serena Williams by beating Ludmilla Samsonova 7-6(8) 6-1 to reach her first quarter-final at Flushing Meadows, joining compatriot Nick Kyrgios.
Wimbledon finalist Nick Kyrgios knocked out defending champion and world number one Daniil Medvedev 7-6(11) 3-6 6-3 6-2 in the fourth round.
"I'm really glad to finally show the work. It took me 27 years," said Kyrgios, who will take on Karen Khachanov in the quarter-final.
KHACHANOV OUTLASTS CARRENO BUSTA
Karen Khachanov edged twice semi-finalist Pablo Carreno Busta of Spain in a tough five-setter, prevailing 4-6 6-3 6-1 4-6 6-3 to reach his third major quarter-final and first in New York.
GAUFF THROUGH IN STRAIGHT SETS
American teenager Coco Gauff reached her first US Open quarter-final after the 12th seed battled back from a break down in the second set to overcome China's Zhang Shuai 7-5 7-5 and set up a showdown with 17th seed Caroline Garcia of France.
GARCIA BREEZES PAST RISKE-AMRITRAJ
Frenchwoman Caroline Garcia continued her red-hot form with a crushing 6-4 6-1 win over American 29th seed Alison Riske-Amritraj to sweep into her maiden US Open quarter-final.
"I'm trying to be aggressive, go for my shots, even when I'm feeling tight. I'm having fun, yeah," said the 17th-seeded Garcia, who takes on Coco Gauff next.
Fifth seed Casper Ruud ended lucky loser Corentin Moutet's superb run by handing the Frenchman a 6-1 6-2 6-7(4) 6-2 loss to reach the US Open quarter-finals for the first time. Awaiting the Norwegian is 13th seed Matteo Berrettini.
BERRETTINI CLAWS PAST DAVIDOVICH FOKINA
Italian Matteo Berrettini made it five Grand Slam quarter-finals in a row after battling past unseeded Alejandro Davidovich Fokina of Spain 3-6 7-6(2) 6-3 4-6 6-2 at Louis Armstrong Stadium.
