Navarro, who is in the form of her life after reaching the semi-finals in San Diego, converted five of her seven break-point opportunities, while Keys broke serve three times on five chances.
Navarro advances to face former US Open finalist Leylah Fernandez of Canada, who knocked out 13th-seeded Elise Mertens of Belgium 6-3, 6-4.
The event's top two seeds cruised to wins as Ons Jabeur of Tunisia routed the United States' Alycia Parks 6-2, 6-2, and Maria Sakkari of Greece downed Australia's Storm Hunter 6-2, 6-4.
Third-seeded Caroline Garcia of France came from behind to beat Belarus' Aliaksandra Sasnovich 4-6, 7-6, 6-4, and eighth-seeded Ekaterina Alexandrova of Russia eked out a 7-6, 7-6 victory over Poland's Magdalena Frech.
The United States' Sofia Kenin eliminated 12th-seeded Anhelina Kalinina of Ukraine 6-2, 7-6.
Guangzhou Open
Number four seed Lucia Bronzetti of Italy swept past Ya Yi Yang of Taiwan 6-1, 6-0 in an hour flat in first-round action in Guangzhou, China.
Bronzetti broke Yang's serve five times in nine opportunities and won 21 of 27 first-service points while never losing her own serve. Her next opponent will be Japan's Moyuka Uchijima, who outlasted France's Jessika Ponchet 7-5, 3-6, 6-3.
Number three seed Tatjana Maria of Germany also had an easy time in the first round, beating Alexandra Eala of the Philippines 6-3, 6-0.
Daria Saville of Australia rallied past Germany's Anna-Lena Friedsam 3-6, 6-3, 6-1, and Viktoria Hruncakova of Slovakia beat Russian Anna Kalinskaya 7-6, 3-6, 6-3.
Other first-round winners included Viktorija Golubic of Switzerland; Yulia Putintseva of Kazakhstan; and Xiyu Wang, Yue Yuan and Zhuoxuan Bai of China.