The much-trumpeted move is part of Crown Prince Mohammed bin Salman's plan to modernise the conservative petrostate -- but it has been dented by the jailing of female activists who long opposed the driving ban.
Women in Riyadh and other cities began zipping around streets bathed in amber light soon after the ban was lifted at midnight, with some blasting music from behind the wheel.
"I feel free like a bird," said talk show host and writer Samar Almogren as she cruised across the capital.
Television presenter Sabika al-Dosari called it "a historic moment for every Saudi woman" before driving a sedan across the border to the kingdom of Bahrain.
The lifting of the ban, long a glaring symbol of repression, is expected to be transformative for many women, freeing them from dependence on private chauffeurs or male relatives.