Francois Hollande has signed into law the right to gay marriage and adoption for same-sex couples.
Hollande's signing of the bill means the first same-sex marriages could be celebrated in the next fortnight, little more than a year after Hollande pledged marriage equality in his pre-election manifesto.
Protests, both pro and anti-gay marriage, have gripped France in the past 12 months, some ending with clashes between police and activists.
The much-argued law was approved by the French senate and national assembly last month and, despite a late challenge from the country's right-wing parties, was upheld by the Constitutional Council.
The signing of the bill makes France the 14th country in the world to legalise gay marriage, and the ninth in Europe behind Belgium, Denmark, Iceland, The Netherlands, Norway, Portugal, Spain and Sweden.
On the issue of equal rights for same-sex adopters, the courts were clear that the new bill would not automatically grant the "right to a child".
The law comes at a time when Francois Hollande is suffering with increasingly low approval ratings, the lowest of any recent French president.
A stagnant economy and rising unemployment, now over 10%, ave severely hit Hollande's ratings.
Some 60% of the French public support the bill, but opponents to equal marriage have said they will continue their campaign, with a major rally planned for 26 May in Paris.