The New York-based organisation Human Rights Watch has called on Saudi Arabia to do more to protect Asian domestic workers from mistreatment.
It says some cases amount to slavery, with employers going unpunished for withholding wages, forced confinement, or physical and sexual violence.
HRW says some workers are imprisoned or lashed on spurious charges such as theft, adultery or witchcraft.
Thousands take shelter with the Social Affairs ministry or foreign embassies.
A spokeswoman for Saudi Arabia's National Society for Human Rights said the report was unfair and one-sided.
Saudi households employ an estimated 1.5 million domestic workers, mainly from Indonesia, Sri Lanka, the Philippines and Nepal, as well as other Asian countries and parts of Africa.
The report, entitled As If I Am Not Human: Abuses against Asian Domestic Workers in Saudi Arabia, says efforts to reform laws and improve conditions have fallen far short of protecting domestic workers.
"In the best cases, migrant women in Saudi Arabia enjoy good working conditions and kind employers, and in the worst they're treated like virtual slaves. Most fall somewhere in between," said senior researcher Nisha Varia.
She called on the Saudi government to extend labour law protections to domestic workers and reform the visa regulations.
Under the current sponsorship system, foreigners must obtain their visas through an employer, who frequently takes possession of the passport.
Employees therefore cannot move jobs, leave the country or complain about their employers' behaviour.
Human Rights Watch recently campaigned on behalf of an Indonesian maid whose employers had charges against them dropped after severely abusing her.
Nour Miyati, 25, contracted gangrene after allegedly being tied up for a month and left without food in 2005. She had to have several fingers and toes amputated.
Human Rights Watch said the ruling "sends a dangerous message to Saudi employers that they can beat domestic workers with impunity and that victims have little hope of justice".
Rights organisations say many foreign domestic maids in Saudi Arabia work in harsh circumstances and often suffer abuse by their employers.
The Saudi Labour Ministry has acknowledged some problems, but the government also says foreign workers' rights are protected under Islamic law.