The group Jabhat Fateh al-Sham said on its Twitter account that commander Abu Omar Sarakeb died in an air strike in Aleppo province, the BBC wrote.
It did not say which country's forces had carried out the air strike.
Al-Nusra Front changed its name at the end of July, reportedly cutting ties with al-Qaeda at the same time.
Jabhat Fateh al-Sham, which has its stronghold in Idlib province, is one of the most powerful jihadist rebel groups and has been fighting the Syrian government since early 2012.
It is considered a terrorist group by the U.S., as well as by Syria and Russia, and was excluded along with the so-called Islamic State (IS) from a U.S.-Russia-brokered partial ceasefire earlier this year.
Read alsoTurkey, U.S. ready to invade IS capitalA source quoted by Reuters said that Abu Omar Sarakeb and others had been targeted in a hideout in the village of Kafr Naha, west of Aleppo city.
Unconfirmed reports said several other senior figures in the group were killed or injured, Reuters reported.
The Syrian Observatory for Human rights, a UK-based group which draws its information from activists on the ground, said an air strike from unknown warplanes had hit a meeting of Jabhat Fateh al-Sham, killing Sarakeb and another military commander named as Abu Muslem al-Shami.