France's top court ruled Friday that a bill permitting same-sex marriage and allowing gay couples to adopt children adheres to the constitution.
President Francois Hollande is expected to sign the bill into law on Saturday.
After the lower house of Parliament, dominated by Hollande's governing Socialist Party, passed the bill last month, conservative and centrist senators filed a legal challenge with the court, the Constitutional Council.
The legislation admits France to a small but growing club.
Lawmakers in New Zealand this year made it the first country in the Asia-Pacific region to legalize same-sex marriage. The law is set to be enacted later this year.
Its move came a week after Uruguayan lawmakers approved a measure allowing same-sex marriage. The measure awaits the signature of Uruguay's president, who has indicated he supports it.
If and when the laws in New Zealand, Uruguay and France are enacted as expected, the count of nations allowing same-sex marriage will rise to 14.
France would be the ninth country in Europe to allow same sex marriage.
The first same-sex couples walked down the aisle in the Netherlands in 2001, with others following suit in Canada, South Africa, Belgium and Spain. Argentina was the first Latin American nation to legalize such marriages, in 2010. Other countries on the list are Denmark, Iceland, Norway, Portugal and Sweden.
Many countries remain split over the issue. A Brazilian court this week issued a directive removing a barrier that had limited same-sex marriage, but no bill has made it through Congress.
Legislators in the United Kingdom are also weighing proposals to legalize same-sex marriage. Lawmakers in Australia voted against a bill to legalize same-sex marriage last September. A poll for the advocacy group Australian Marriage Equality indicated that 64% of those surveyed "support marriage equality."
In the United States, the question went before the Supreme Court and justices are now deliberating over the matter.
Twelve U.S. states and the District of Columbia have legalized same-sex marriages. On the other side, many states have specific laws blocking same-sex couples from legally marrying.