On October 7, Hamas and other Palestinian militants stormed into southern Israel, killing some 1,200 people and capturing more than 240.
Israel's air and ground war in response has reportedly killed more than 18,000 Palestinians, including women and children, and injured almost 50,000. Some 1.9 million people have also been forced to flee their homes.
Hamas have continued to battle a barrage of missile attacks from Israel as its offensive in Gaza continues, urged by Israeli Prime Minister Benjamin Netanyahu.
But who are Hamas' most prominent figures manning the helm through what has become the territory's deadliest-ever war?
Ismail Haniyeh is largely considered the supreme leader of the Hamas militant group.
He was born in the Al-Shati refugee camp in the Gaza Strip in 1962, and later studied Arabic literature at the Islamic University of Gaza. It was at university where Haniyeh first became involved with Hamas.
Israel imprisoned Haniyeh for three years in 1989. After this, he was exiled to a desolate area between Israel and Lebanon, alongside a number of Hamas leaders.
In 1997, he was appointed to head a Hamas office.
He was head of the Hamas list that won the Palestinian legislative elections of 2006, becoming Prime Minister of the State of Palestine.
However, then-President Mahmoud Abbas dismissed Haniyeh from office on June 14, 2007, at the height of the conflict between Abbas' Fatah party and Hamas.
Haniyeh did not acknowledge the decree and continued to exercise prime ministerial authority in the Gaza Strip.
He was replaced by Yahya Sinwar as leader of Hamas in Gaza in 2017, when he was elected head of the group's political bureau.
In 2018, the US Department of State designated Haniyeh a terrorist.
He now lives in Qatar but has become the tough-talking face of Hamas' international diplomacy.
Saleh Arouri was the deputy chairman of Hamas' political bureau, a decision-making group that determines social, political and military policy.
He was widely considered Hamas' deputy leader before he was killed on January 2 in a blast in Beirut.
Arouri was a founder of Hamas' military wing and had headed up the group's presence in the West Bank.
Israel’s Prime Minister Benjamin Netanyahu had threated to kill him even before the Hamas-Israel conflict broke out on October 7, but Israeli officials declined to comment on Arouri's death.
The mastermind of the Hamas attack on Israel is a secretive figure, feared on both sides of the battle lines.
Yahya Sinwar is Hamas’ top leader inside the Palestinian territory, a rarely seen veteran militant who learned fluent Hebrew during his years spent in Israeli prisons.
He was born in 1962 in Gaza’s Khan Younis refugee camp to a family that was among thousands of Palestinians driven from what is now the city of Ashkelon during the 1948 war surrounding Israel's creation.
He was an early member of Hamas as it emerged from the Palestinian branch of the Muslim Brotherhood in 1987.
Sinwar convinced the group’s founder, Sheikh Ahmed Yassin, that to succeed as a resistance organisation, Hamas needed to be purged of spies for Israel. They founded a security arm, then known as Majd, which Sinwar led.
Arrested by Israel in the late 1980s, he admitted under interrogation to having killed 12 suspected collaborators.
He was eventually sentenced to four life terms for offenses that included the abduction and killing of two Israeli soldiers.
He became the leader of the hundreds of imprisoned Hamas members, organising strikes to improve conditions as he learned Hebrew and studied Israeli society.
In 2008, Sinwrar survived an aggressive form of brain cancer after treatment at a Tel Aviv hospital.
Netanyahu released him in 2011 along with about 1,000 other prisoners in exchange for Gilad Schalit, an Israeli soldier captured by Hamas in a cross-border raid.
Back in Gaza, Sinwar closely coordinated between Hamas’ political leadership and its military wing, the Qassam Brigades.
In 2017, he was elected head of Hamas’ political bureau in Gaza.
Sinwar worked with Haniyeh to realign the group with Iran and its allies, including Lebanon’s Hezbollah. He also focused on building Hamas' military power.
Israeli officials have vowed to kill him and crush his entire militant group. But over two months into the war, the 61-year-old remains alive, in hiding.
In September 2015, Sinwar was designated a terrorist by the United States government.
Perhaps even more elusive than Sinwar, Mohammed Deif is the head of Hamas' military wing, the Izz al-Din al-Qassam Brigades.
He was also imprisoned him by Israeli authorities in 1989, after which he formed the al-Qassam Brigades in a bid to capture Israeli soldiers.
After his release, he is said to have been one of the masterminds behind the construction of tunnels that have allowed Hamas fighters to get inside Israel from Gaza. He was imprisoned again in 2000 but later escaped.
Deif, like Sinwar, lives in the shadows having avoided seven assassination attempts on his life before 2021.
They have cost him an eye and left him with a serious leg injury, according to military officials in Israel.
But his ability to evade the Israeli authorities have earned him the nickname "the man with nine lives".
An Israeli air strike in 2014 killed his wife, his three-year-old daughter and seven-month-old son.
There now exists little photographs or footage of Deif - one of the few photos that is in circulation shows only his shadow.
The US' Department of State added Deif to its list of Specially Designated Global Terrorists in 2015.
Marwan Issa is Deif's deputy commander-in-chief.
Some sources have claimed Issa was named the group’s leader following the death of Ahmed Jaabari in an Israeli attack in 2012.
However, Issa remains Deif's second-in-command at the the Izz al-Din al-Qassam Brigades while serving as a representative for the Brigades in Hamas' political bureau.
He was detained by Israeli forces him during the first Palestinian uprising for five years due to his activity with Hamas.
He was arrested again by The Palestinian Authority in 1997, but was freed after the second intifada in 2000.
His brother was killed in an Israeli airstrike in 2021, and Issa was designated as a terrorist by the US in 2019.
One of Hamas' founders, Mashal became the leader of the Kuwaiti branch of the organisation in 1987.
In 1992, he became a founding member of Hamas' political bureau and its chairman.
He became the recognised head of Hamas after Israel assassinated both Sheikh Ahmed Yassin and his successor Abdel Aziz al-Rantisi in the spring of 2004.
Under his leadership, Hamas stunned the world by winning a majority of the seats in the Palestinian legislative election in 2006.
Mashal stepped down as Hamas' politburo chairman at the end of his term limit in 2017.
He has lived in other parts of the Arab world in exile. For that reason, he was considered part of Hamas' "external leadership".
Want a quick and expert briefing on the biggest news stories? Listen to our latest podcasts to find out What You Need To Know...