Despite warnings by police and ultraconservatives in the kingdom against defying the ban, at least four women have successfully driven, May Al Sawyan said.
Though no specific Saudi law bans women from driving, women are not issued licenses. Powerful clerics who hold far-reaching influence over the kingdom's ruling monarchy enforce the ban. Clerics warn that "licentiousness" will spread if women drive.
In the run-up to the campaign, police warned that anyone disturbing public order would be dealt with forcefully.
The account's website, oct26driving.Org, and official English language YouTube account were hacked on Friday, according to activists.
Activists posted a four minute-long video on the campaign's official Arabic account that they said depicted Al Sawyan driving in Riyadh.
She wore sunglasses and her hair was covered by the traditional black headscarf worn by Saudi women, but her face was otherwise visible.
Like other female drivers defying the ban in Saudi Arabia, Al Sawyan said she has obtained a driver's license from abroad.
"There were some cars that drove by. They were surprised, but it was just a glance. It is fine ... They are not used to seeing women driving here."
However, Al Sawyan said she was prepared for the risk of detention if caught. She said she was far enough from a police car that she was not spotted.
"I just took a small loop. I didn't drive for a long way, but it was fine. I went to the grocery store," she said. Her husband and family waited at home and called her nervously when she arrived at the grocery store to check on her, she said.
The kingdom's first major driving protest came in 1995. Some 50 women who drove their cars were jailed for a day, had their passports confiscated and lost their jobs.
In June 2011, about 40 women got behind the wheel in several cities in a protest sparked when a woman was arrested after posting a video of herself driving.
