Salma bint Hizab al-Oteibi won a seat in Mecca province in Saturday’s vote.
Women have also won in several other regions in the country, including Jeddah and Qatif, reports suggest.
The election was the first where women were allowed to vote and stand as candidates, and is being viewed as a landmark in the conservative kingdom.
Saudi women still face many curbs in public life, including driving.
A total of 978 women registered as candidates, alongside 5,938 men.
Officials said about 130,000 women had registered to vote in Saturday’s poll, compared with 1.35 million men.
The disparity was attributed by female voters to bureaucratic obstacles and a lack of transport, the AFP news agency says.
Female candidates were also not allowed to address male voters directly during campaigning. Turnout was high, state media reported.
Ms Oteibi won a seat on the council in Madrakah in Mecca province, the president of the election commission, Osama al-Bar, told the official SPA news agency.
She was running against seven men and two women, Mr Bar was quoted as saying.
Elections of any kind are rare in the Saudi kingdom – Saturday was only the third time in history that Saudis had gone to the polls.
There were no elections in the 40 years between 1965 and 2005.
The decision to allow women to take part was taken by the late King Abdullah and is seen as a key part of his legacy.
In announcing the reforms, King Abdullah said women in Saudi Arabia “have demonstrated positions that expressed correct opinions and advice”.
Before he died in January, he appointed 30 women to the country’s top advisory Shura Council.
There were 2,100 council seats available in Saturday’s vote. An additional 1,050 seats are appointed with approval from the king.