The activist in her late 20s is among the most outspoken women's rights activists in the kingdom.
She was detained for more than 70 days after she attempted to livestream herself driving from neighboring United Arab Emirates to Saudi Arabia in 2014.
She was detained by Saudi authorities as she attempted to cross the border and referred to an anti-terrorism court on charges of criticizing the government online.
She was later released without trial. Activists say al-Hathloul was arrested again in June of last year in connection with her advocacy.
Activists say al-Hathloul was then stopped by authorities in Abu Dhabi, where she was residing, and transferred to Saudi Arabia earlier this year where she's been under a travel ban since March.
Al-Hathloul attended a humanitarian summit in Canada in 2016, where she was photographed in Vanity Fair magazine with former American actress Meghan Markle, who wed Prince Harry over the weekend.
A retired professor at King Saud University, al-Yousef is a mother of five and a grandmother of eight.
Although she hails from a conservative tribe with links to the royal family, she is among the most prominent women's rights activists in Saudi Arabia.
In 2016, she delivered a petition signed by thousands to the royal court calling for an end to guardianship laws that give male relatives final say over a woman's ability to marry or travel abroad.
She has worked for years assisting women fleeing abusive marriages and homes. She also defied the kingdom's ban on women driving on several occasions.
'This is a good step forward for women's rights,' al-Yousef told The Associated Press last year when the kingdom announced that women would be allowed to drive. However, she cautioned it was just 'the first step in a lot of rights we are waiting for.'
An assistant professor of linguistics and a mother of three, including a toddler, al-Nafjan runs one of the first English blogs on Saudi Arabia.
She describes the 'Saudiwoman' blog as an effort to counter the many non-Saudis and non-Arabs 'out there giving 'expert' opinions on life and culture' in the kingdom.
Al-Nafjan has protested the driving ban, including publicly driving in the capital, Riyadh, in 2013 as part of a campaign launched by women's rights activists.
She has worked closely with al-Yousef and other women's rights activists to help domestic abuse victims and bring attention to repressive guardianship laws.
In recent years, she has been cautious about voicing her opinion on Twitter out of concern over a growing crackdown on rights advocates.
She was among dozens of women who were warned by the royal court last year to stop speaking with the press or voicing opinions online.
A psychotherapist in her mid-60s, al-Ajroush runs a private therapy practice in the capital, Riyadh, which specializes in gender orientation, according to activists.
She helped initiate a nationwide program in Saudi Arabia to provide support for domestic abuse victims and train police and courts on how to receive and treat such victims.
A longtime advocate of women's rights, she took part in the kingdom's first driving protest in 1990 and subsequent campaigns to end the ban on women driving.
She has faced years of harassment by authorities, including house