Haniya replaces Qatar-based veteran leader Khaled Meshaal, who steps down at the end of his two terms in office.
The Palestinian movement Hamas on Saturday elected Ismail Haniya to lead its political office, the group's spokesman Fawzi Barhoum announced.
Former deputy chief Haniya will replace Qatar-based veteran leader Khaled Meshaal, who steps down at the end of his term limit and as Hamas looks to rebrand its image with a new manifesto and a more moderate stance towards Israel.
"The Hamas Shura Council on Saturday elected Ismail Haniya as head of the movement's political bureau," the group's official website announced.
He beat contenders Mussa Abu Marzuk and Mohamed Nazzal in a video conference vote of the ruling council's members in Gaza, the West Bank and outside the Palestinian territories.
Gaza-born Haniya, 54, served as Palestinian prime minister after the group's victory in 2006 polls and continued to claim the title despite being officially sacked by Palestinian president and Fatah chief Mahmoud Abbas.
Hamas has been governing the Gaza Strip since seizing the coastal territory in 2007 from the rival Fatah party based in the West Bank and has fought three wars with Israel.
But the group dropped its longstanding call for Israel's destruction and severed ties with the Muslim Brotherhood in its policy shakeup announced at its main overseas office in the Qatari capital Doha last week.
The move, dismissed by Israel, appeared aimed at improving ties with Gulf states and Egypt as Abbas visited new US President Donald Trump in Washington, who expressed interest in renewing Israeli-Palestinian peace efforts.
Hamas in its new document agrees to a transitional Palestinian state within frontiers pre-dating a 1967 war but continues to refuse to recognise a right for Israel to exist and backs an "armed struggle," while Abbas recognises Israel and seeks a final peace agreement based on those lines.
TRT World's correspondent Nicole Johnston explains what Haniya's election means.