Deputy leader promoted after Israeli assassinations left the Lebanon-based group in a leadership vacuum.
Hezbollah has announced Naim Qassem as its new head.
Qassem, whose promotion from deputy leader was announced on Tuesday, replaces Hassan Nasrallah as secretary-general of the Lebanon-based armed group.
Nasrallah was killed in Beirut in late September by an Israeli strike. Many other senior Hezbollah officials have also been targeted since Israel turned its focus on the group that month.
In a statement, Hezbollah said Qassem was elected to take up the position due to his “adherence to the principles and goals of Hezbollah”.
It added that the group would “[ask] God Almighty to guide him in this noble mission in leading Hezbollah and its Islamic resistance”.
Vacuum
The killing of Nasrallah, who embodied the Lebanese Shia movement in the eyes of its supporters and the wider region, was seen as having left a vacuum inside a group that had already lost much of its leadership as a result of months of Israeli assassinations.
Nasrallah’s cousin Hashem Safieddine was previously viewed as the favourite to take the helm of the Iran-linked Hezbollah, but he died in an Israeli strike on Beirut shortly after his relative.
The 71-year-old Qassem has often been referred to as Hezbollah’s “number two”. He is one of the religious scholars who founded the group in the early 1980s and has a long history in Shia political activism.
He was the most senior Hezbollah official to continue making public appearances after Nasrallah largely went into hiding following the group’s 2006 war with Israel.
Since the former leader was killed, Qassem has made three televised addresses, speaking in more formal Arabic than the colloquial Lebanese favoured by Nasrallah.
On September 30, he issued a defiant message, saying that Hezbollah remains ready to fight Israel and to win.