Her trouble with the authorities comes less than two weeks after Saudi Arabia executed 47 men, including an outspoken Shiite cleric, Sheikh Nimr al-Nimr. While the government accused him of inciting violence against the police, rights groups said he was executed for his fiery sermons that called for the downfall of the royal family.

Ms. Badawi did not advocate anything like that, but did push for more rights for women in a country that bars them from marrying, traveling abroad and getting some medical procedures without the permission of a male guardian.

In 2012, the State Department gave Ms. Badawi an International Woman of Courage Award. Hillary Clinton, then the secretary of state, said that she was the first woman to sue her guardian for preventing her from marrying the man of her choice, and also sued the Saudi government for the right to vote in municipal elections.

In 2014, the Saudi government barred Ms. Badawi from traveling outside the kingdom. On Tuesday, she was arrested with her 2-year-old daughter in Jidda, according to a statement by Amnesty International citing Saudi activists.

It remained unclear why Ms. Badawi had been detained and whether she would be charged with a crime. In a text message, Maj. Gen. Mansour Turki, a spokesman for the Saudi Interior Ministry, denied that Ms. Badawi had been arrested but said she was being interrogated in a police station in connection with a request from a prosecutor.