"The first point is a very clear red line to ban any kind of use of chemical weapons, and any use of chemical weapons will be retaliated by France," Macron said, standing next to Putin before reporters at the palace of Versailles, near Paris.
Macron said he hopes the two countries can work together in bringing peace and a "democratic transition" to Syria.
His use of the phrase "red line" echoed comments made by former US President Barack Obama in 2012. Obama said Syrian President Bashar al-Assad would risk crossing a "red line"
and provoking a US military response by using or moving chemical or biological weapons.
Obama decided against striking in 2013 after a chemical attack.
Last month, US missiles targeted the Shayrat airfield i
n western Syria. That strike was a response to a chemical attack widely blamed on Assad's regime.
Monday's meeting between Macron and Putin was the first since Macron was sworn in as president May 14.
Macron slams Russian media outlets
Macron also decried two Russian state-financed media outlets -- Russia Today and Sputnik
-- for spreading "lies" during his presidential campaign against far-right candidate Marine Le Pen
"Some press bodies did indeed interfere with my campaign," Macron said. "Sputnik and Russia Today did not behave like the press, but like influence and propaganda organizations to me."
Le Pen visited Moscow "regularly," Putin said.
"I am prepared to welcome anybody always," he said.
"If Marine Le Pen wanted a visit, why should I refuse her?"
Treatment of gays discussed
Witnesses and victims have told CNN
that hundreds of gay men were being rounded up by authorities and held in detention centers.
"I reminded him of the importance for France of the respect of all peoples and all minorities, all sensibilities in civil society," Macron said of Putin.
"We mentioned the LGBT (lesbian, gay, bisexual and transgender) organization in Chechnya but also the (organizations) in Russia. And on that subject, I very precisely pointed out to President Putin the expectation of France.
"President Putin pointed out moreover that he had actually taken some initiatives with regard to the LGBT population in Chechnya and is trying to get to the bottom of what is happening."