Hollande made "marriage for all" a central plank of his presidential election campaign last year. On Friday, he tried to turn the page on months of bitter opposition to the measures, arguing it was "time to respect the law and the Republic".
And he warned that he would tolerate no resistance.
"I will ensure that the law applies across the whole territory, in full, and I will not accept any disruption of these marriages," said the president.
French Justice Minister Christiane Taubira, who steered the legislation through parliament, has said the first gay marriages could be celebrated as early as June.
Marriages in France must take place in town halls, most of which take around four weeks to process marriage applications.
The issue of gay marriage and adoption has provoked months of acrimonious debate and hundreds of protests that have occasionally spilled over into violence and is unlikely to drop off the political agenda.
Although the Constitutional Council approved the bill , the International Day Against Homophobia, its opponents have vowed to fight on.Felicitations!