Information from 57 countries, most of which are in sub-Saharan Africa, revealed that only around half of adolescent girls and women can make decisions "that underpin bodily autonomy and integrity."
These include the freedom to independently choose whom to have sex with or use contraception, according to the report published by the UN population fund UNFPA.
UNFPA chief Natalia Kanem labelled the findings as "outrageous," saying that in essence "hundreds of millions of women and girls are not the owners of their own bodies" and that their lives are ruled by other people.
In the report, Kanem states that conditions for many women have worsened due to the coronavirus pandemic.
"Right now, for instance, record numbers of women and girls are at risk of gender-based violence and harmful practices such as early marriage," she said.
Kanem has urged the international community to be more committed to gender equality.
Despite "constitutional guarantees" of gender equality in many countries, on average, women enjoy just 75 per cent of the legal rights of men, the report states, citing 2020 figures from the UN Secretary-General.