Macron told a joint press conference with the Lebanese prime minister that he wishes to organise a conference on Syrian refugees, "involving all the countries in the region that have taken in refugees", in the first quarter of 2018.
The conference could take place in Beirut, he added.
Some 1.2 million Syrian refugees are now living in Lebanon, whose population is just over six million.
They "weigh heavily on the economy, the environment and security", Hariri said.
Macron also promised to organise a conference of big international investors, including the World Bank, in Paris to help revive Lebanon's economy and said he had invited President Michel Aoun to a state visit to Paris, the first of his presidency.
Lebanon is planning to hold its first parliamentary election for nine years next year.
Confusion over Assad
In an interview with Le Monde newspaper ahead of meeting Macron, Hariri declared that "obviously" Syrian President Bashar al-Assad "must go".
"If the international community wants a long-term solution in Syria, it's the only way out," he said. "While he's there there will be no stability. This regime does not control its territory. It's Russia and Iran that control it."
He warned that "The refugees will not return while the regime is in place" and predicted that "without a credible political solution ... there will be even worse than Daesh [the Islamic State armed group].
Earlier this year Macron appeared to change France's position, declaring that Assad's departure is not a "prerequisite" for peace.
At the press conference Macron said that he did not want to get "bogged down in that debate".
But on Monday he said that crimes committed during the conflict, "notably by this country's leaders", should be judged, while Foreign Affairs Minister Jean-Yves Le Drian on Friday seemed to revive France's demand that Assad quit office.