Iceland, Finland and Norway top the list of 136 nations, based on political participation, economic equality and rights like education and health.
The Middle East and North Africa were the only regions not to improve in the past year, with Yemen at the bottom.
The Philippines and Nicaragua both feature in the top 10.
The WEF has produced the report annually for the past eight years.
One hundred women from all around the world are gathering for a day of debate and discussion as the 100 Women season comes to an end.
Iceland’s position at the top of the WEF rankings was the fifth year in a row the country has been named the world’s most equal.
Report founder and co-author Saadia Zahidi told the BBC that since the WEF began compiling the index in 2006, 80% of countries had made progress.
“What’s worrying though is that 20% of countries have made no progress or are falling behind,” she said.
Nadia al-Sakkaf, editor of the English-language Yemen Times, in London for the 100 Women conference, told the BBC that she had stopped counting the years her country had languished at the bottom of the equality list.
“It comes down to everyday life. We had three women running for president in 2006. We have lots of women in senior positions,” she said.
“But our levels of maternal mortality are very high, and 35% of girls aged 6-14 years old are not in school.”
Saadia Zahidi of the WEF said that by contrast many sub-Saharan countries had not invested in women, but through necessity they played a major role in the economy.
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