Police estimate that up to 150,000 people joined marches that converged on the city centre, but organisers put the figure close to one million.
Clashes erupted after the rally finished between far-right activists and riot police. The authorities said nearly 100 people were arrested.
On Saturday 50 people were detained for blocking the Champs-Elysees.
The same-sex marriage bill, which also legalises gay adoption, was signed into law by President Francois Hollande last week, after months of heated debate.
Huge anti-gay marriage protest in Paris
27 May 2013
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Tens of thousands of people have rallied in Paris against a new French law allowing same-sex marriage.
