The UN Population Fund's annual State of World Population report said "gender apartheid" could scuttle the global body's goal of halving extreme poverty by 2015.
"We cannot make poverty history until we stop violence against women and girls," the fund's executive director, Thoraya Ahmed Obaid, said at the report's launch in London on Wednesday.
"We cannot make poverty history until women enjoy their full social, cultural, economic and political rights."
The report said gender equality and better reproductive health could save the lives of two million women and 30 million children over the next decade - and help lift millions around the world out of poverty.
In 2000, the UN agreed to eight Millennium Development Goals, which include halving extreme poverty, achieving universal primary education and stemming the Aids pandemic, all by 2015.
The report said one of the targets - promoting gender equality and empowering women - is "critical to the success of the other seven".
Gender discrimination, the report said, lowered productivity and increased health care costs and mortality.
Improving women's educational
opportunities is important
Improving women's political, economic and education opportunities would lead to "improved economic prospects, smaller families, healthier and more literate children, lower HIV prevalence rates and reduced incidence of harmful traditional practices".
But for many women around the world, the UN agency said, the picture remains grim.
It calculated that 250 million years of productive life are lost annually because of reproductive health problems including HIV/Aids, the leading cause of death among women between 15 and 44.
Half the 40 million people infected with HIV around the world are women, and in sub-Saharan Africa women make up a majority of those infected.
Lack of contraception leads to 76 million unintended pregnancies in the developing world and 19 million unsafe abortions around the world each year, the agency said.
"We cannot make poverty history until women enjoy their full social, cultural, economic and political rights"
Thoraya Ahmed Obaid,
UN Population Fund
More than half a million women die each year from preventable pregnancy-related causes, a figure that has changed little in a decade.
One woman in three around the world is likely to experience physical, psychological or sexual abuse in her lifetime.
Many still lack the educational opportunities available to men - 600 million women around the world are illiterate, compared with 320 million men.
Progress too slow
The report said progress had been made in many countries, but was too slow.
Women fill only 16% of parliamentary seats around the world, an increase of 4% since 1990.
Kofi Annan: It's a make-or-break
moment for the millennium goals
The highest rates are in Rwanda - where 49% of parliamentarians are women - and Sweden.
At a UN world summit last month, many were pessimistic about whether the Millennium Development Goals would ever be reached.
Secretary-general Kofi Annan said it was "a make-or-break moment" for the goals.
The UNFPA report said the estimated cost of achieving them - 135 billion in 2006, rising to $195 billion in 2015 - was "modest and feasible".
"In 2003, donor governments spent $69 billion on development aid. That same year, global military spending totalled approximately $1 trillion," the report said.
"Given this disparity, it is clear that the cost of meeting the MDGs is more a matter of political will and commitment than scarce resources."