More than 900 women are standing alongside thousands of men in the December 12 municipal ballot, which will also mark the first time women are allowed to vote.
"I've been eliminated as a candidate for the municipal elections," Loujain Hathloul said in a tweet.
Saudi authorities detained Hathloul for more than two months after she tried to drive into the kingdom last December from the United Arab Emirates, in defiance of a Saudi ban on female motorists.
Another driving activist, Tamadour al-Yami, told AFP her name was also dropped from the final list of authorised candidates. She vowed to appeal, "but I don't think it will change anything."
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And Nassima al-Sadah, a human rights activist and would-be candidate in the Gulf coast city of Qatif, said officials informed her yesterday that her name had been removed.
"I don't know why," said Sadah, who was trained in electioneering by the National Democratic Institute, a Washington non-profit organisation.
Ruled by King Salman, oil-rich Saudi Arabia has no elected legislature and has faced intense Western scrutiny over its rights record.
From restaurants to banks, offices -- and election facilities -- the sexes are strictly segregated in the kingdom.
"We will vote for the women even though we don't know anything about them," Um Fawaz, a teacher in her 20s, said in Hafr al-Batin city.
"It's enough that they are women," she said.
The absolute monarchy, which applies a strict interpretation of Islam, has faced widespread criticism for a lack of equal rights.
Saudi Arabia is the only country in the world where women are not allowed to drive.