She was arrested during an overnight raid on her home in the occupied West Bank.
The Israeli military said she was arrested on suspicion on “inciting violence and calling for terrorist activity to be carried out”.
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Sky News report of Ahed Tamimi being arrested in 2017
It comes after an Instagram post was published in her name calling for the “slaughter” of Israeli West Bank settlers.
However, Ms Tamimi’s family said she does not have an Instagram account and the post was a fake.
The post is no longer visible online, nor is the account carrying Ms Tamimi’s name and photo where it was published last week.
Her mother, Nariman Tamimi, said more than a dozen Israeli soldiers entered their house in Nabi Saleh village on Monday, ransacked their possessions and then took her daughter away.
She said Israeli forces had accused Ms Tamimi of “calling for the killing of settlers and saying what Hitler did wasn’t enough – but Ahed does not have an Instagram account”.
Supporters have claimed the online post was an excuse to arrest the activist and crackdown on dissent while the world is distracted by the conflict in Gaza.
Israel’s national security minister Itamar Ben Gvir congratulated security forces for arresting Ms Tamimi, who he described as a “terrorist” on X, formerly known as Twitter.