Women cannot make even simple decisions on children, the report says
Saudi women are being kept in perpetual childhood so male relatives can exercise "guardianship" over them, the Human Rights Watch group has said.
The New York-based group says Saudi women have to obtain permission from male relatives to work, travel, study, marry or even receive health care.
Their access to justice is also severely constrained, it says.
The group says the Saudi establishment sacrifices basic human rights to maintain male control over women.
Saudi Arabia is the only country in the world where women are not allowed to drive.
Saudi clerics see the guardianship of women's honour as a key to the country's social and moral order.
The report, Perpetual Minors: Human Rights Abuses Stemming from Male Guardianship and Sex Segregation in Saudi Arabia, draws on more than 100 interviews with Saudi women.
Farida Deif, women's rights researcher for the Middle East at Human Rights Watch, said: "Saudi women won't make any progress until the government ends the abuses that stem from these misguided policies."
It's astonishing that the Saudi government denies adult women the right to make decisions for themselves but holds them criminally responsible for their actions at puberty
Human Rights Watch
The report says that Saudi women are denied the legal right to make even trivial decisions for their children - women cannot open bank accounts for children, enrol them in school, obtain school files or travel with their children without written permission from the child's father.
Human Rights Watch says that Saudi women are prevented from accessing government agencies that have no established female sections unless they have a male representative.
The need to establish separate office spaces for women is a disincentive to hiring female employees, and female students are often relegated to unequal facilities with unequal academic opportunities, the report says.
Male guardianship over adult women also contributes to their risk of exposure to violence within the family as victims of violence find it difficult to seek protection or redress from the courts.
Social workers, physicians and lawyers say that it is nearly impossible to remove guardianship from male guardians who are abusive, the group says.
"It's astonishing that the Saudi government denies adult women the right to make decisions for themselves but holds them criminally responsible for their actions at puberty," said Ms Deif.
"For Saudi women, reaching adulthood brings no rights, only responsibilities."