A Russian Antonov 124 military cargo plane carrying 50 tons of medical aid and humanitarian supplies left the airport at the central French city of Chateauroux at 3am (0100 GMT), the airport's head Mark Bottemine told AFP.
Undertaken as part of a UN Security Council resolution, "the aim of this project is to enable civilian populations better access to aid," a joint Franco-Russian statement said.
The plane is heading for Russia's Hmeimim air base in the west of Syria. It is the first joint humanitarian aid operation between Russia and a western country.
The aid will be distributed on Saturday under the supervision of the UN's Office for the Coordination of Humanitarian Aid (OCHA).
"Humanitarian assistance is an absolute priority and must be distributed in accordance with principles of humanity, neutrality, impartiality and independence across all Syrian territory without exception, where international humanitarian law must be fully respected," the joint statement said.
France had secured "guarantees" from Russia that the Syrian regime would not obstruct the distribution of the aid, and that it would not be misappropriated or diverted for political purposes, the foreign ministry said.
More than 1,700 civilians were killed during the Syrian regime's operation in Eastern Ghouta in March and April. According to the Russian military, more than 160,000 people, both military and civilians, were evacuated from the region.
The cargo comprises medical equipment, tents, cooking utensils and blankets, said an AFP photographer who witnessed the plane being loaded.
The medical aid is aimed at some 500 people who have been seriously injured and the 15,000 others who have lighter injuries during the fighting in Eastern Ghouta, on the fringes of the Syrian capital Damascus.