Charbonnier, known as "Charb", was 47. He had received death threats in the past and had been under police protection.
Reports say he was in an editorial meeting with the others when two masked gunmen burst in and opened fire with Kalashnikov assault rifles. The gunmen reportedly shouted "Allahu akbar!" (God is great).
The left-wing magazine's famous cartoonists went by nicknames - the others who died were called Cabu, Tignous and Wolinski.
Charb had strongly defended Charlie Hebdo's cartoons featuring the Prophet Muhammad.
"Muhammad isn't sacred to me,'' he told the Associated Press in 2012, after the magazine's offices had been fire-bombed.
"I don't blame Muslims for not laughing at our drawings. I live under French law. I don't live under Koranic law."
In 2007 Charlie Hebdo also defended itself in court over cartoons of the Prophet Muhammad, reprinted in the magazine, which had angered Muslims.
But Charlie Hebdo's anti-establishment satire was wide-ranging - it included poking fun at the far right, and aspects of Catholicism and Judaism.
Stephane Charbonnier, editor of the French satirical magazine Charlie Hebdo, was among four cartoonists killed in the Paris massacre which left 12 people dead in total.