Several thousand people demonstrated in Paris on Saturday under the rallying cry "Stop the massacre in Gaza".
The left-wing organisers called for France to "demand an immediate ceasefire" between Israel and Hamas militants.
"I came to support the Palestinian cause, for a ceasefire in Gaza," said engineer Ahlem Triki, a Palestinian flag over her shoulders.
Hamas's shock October 7 attack killed about 1,200 people, mostly civilians, in Israel and 239 people taken hostage, according to Israeli officials.
The Israeli air and ground military campaign in response has left more than 11,000 people in Gaza dead, according to the Hamas-run health ministry.
"It is elementary that as activists or simple citizens, you go out on to the street to support the Palestinian people," said 85-year-old trade unionist Claude Marill.