The Israeli military said Mohammad Odeh was killed in an operation in Gaza on Tuesday.
A relative of Odeh confirmed his death to Reuters and said the funeral would take place after noon prayers in Gaza City.
Hamas has yet to issue an official statement, but a statement from his family said he was killed along with his wife and son.
Gaza health officials said six people, including at least one woman, were killed and more than 20 others were wounded in the same Israeli strike that destroyed an upper floor of an apartment building in the Rimal neighbourhood in Gaza City.
Rescue workers were still at the scene looking for more possible casualties.
Israeli Prime Minister Benjamin Netanyahu said on Tuesday that Odeh had headed Hamas' intelligence division at the time of the October 7, 2023 cross-border attack into Israel that triggered the Gaza war and was appointed about a week ago to replace Izz al-Din al-Haddad, the group's chief armed commander, who was killed by Israel on May 15.
Sources close to Hamas did not confirm Odeh's appointment as the new military chief but agreed he was seen as Haddad's possible successor, as the group's chief of military intelligence and possibly the last remaining living member of the armed wing's higher leadership council.
Hours before the attack, Israel announced it had expanded ground operations in Lebanon, where it has been fighting Iran-allied Hezbollah militants since it launched attacks on Iran with the United States at the end of February.
Israel is also intensifying its military activities in the West Bank.
Israel and Hamas are deadlocked in indirect talks over implementing the second phase of a ceasefire deal, which includes the group's disarmament and Israeli army withdrawals.
The ceasefire agreed in October left Israel in control of more than half of Gaza, with Hamas controlling a sliver of coastal territory.
In a statement, Israeli Defense Minister Israel Katz said Hamas would no longer exercise civilian or military control over Gaza and that a plan for what he described as "voluntary migration" from the enclave would also be implemented "at the right time and in the right way".
Some 900 Palestinians have been killed in Israeli strikes since the truce came into effect, according to figures from Gaza health officials that do not distinguish between combatants and civilians.
Four Israeli soldiers have been killed by militants during the same period, the country's military has said.
Israel has killed dozens of Hamas leaders and military officials since the start of the Gaza war, and has vowed to kill or capture anyone who it says was involved in the October 7, 2023 attacks.
Hamas does not disclose figures for casualties among its fighters. Israel says its post-ceasefire strikes are aimed at preventing attacks or stopping people from approaching its armistice line with Hamas.
More than 72,000 Gazans have been killed since the war started in October 2023, most of them civilians, according to Gaza health authorities. Israel says it takes extraordinary measures to avoid civilian casualties.
Hamas' October 7, 2023, attacks on Israel killed 1200 people, according to Israeli tallies.
