IS leader Abu Bakr al-Baghdadi's death marks the end of one of the world's most most brutal jihadi leaders.
Al-Baghdadi commanded tens of thousands of fighters from around the world and carved a territorial caliphate in the Middle East.
US president Donald Trump announced al-Baghdadi was killed after he was chased into a tunnel by US forces, where he blew himself and three of his children up with a suicide vest.
IS lost its last section of territory earlier this year to US-backed Kurdish forces, but al-Baghdadi continued to order his forces to carry out attacks.
His death marks a blow to the so-called caliphate but the group has survived the loss of previous leaders and military setbacks going back to the aftermath of the US-led invasion of Iraq in 2003.
Here is what his death means for IS.
Who was Abu Bakr al-Baghdadi?
Born Ibrahim Awwad Ibrahim Ali al-Badri al-Samarrai in 1971 in Samarra, Iraq, he adopted the nom de guerre al-Baghdadi early on and joined the Sunni insurgency against US forces after the 2003 invasion.
He was detained by US troops in February 2004 and spent 10 months in the Camp Bucca prison in southern Iraq.
He eventually took control of group the so-called Islamic State of Iraq, an al-Qaeda-linked group founded by Abu Musab al-Zarqawi, a Jordanian militant killed in a US air strike in Iraq in 2006.
Under Baghdadi's leadership, IS - or Daesh - expanded into Syria, exploiting the chaos of the country's 2011 uprising and civil war.
In 2014, his fighters swept across eastern Syria and northern and western Iraq, carving out a "caliphate" in a third of both countries.
In early July 2014, al-Baghdadi made his first public appearance, delivering a sermon in a centuries-old mosque in Mosul and declared himself caliph, or the leader of the world's Muslims.
Under his reign, the group carried out horrific acts, including the rape of thousands of Yazidi women, beheadings of Westerners and throwing people they suspected of being gay off buildings.
The cult gleefully broadcast their heinous crimes on social media for the world to see.
What threat did al-Baghdadi pose?
He repeatedly called on followers to carry out attacks on enemies, including the US and other Western nations.
He also called for attacks on Shiite Muslims, who he deemed apostates, and even devout Sunni Muslim's who rejected his extremist views.
Baghdadi called on followers to use whatever weapons they had, and the group claimed scores of attacks worldwide, including on lone-wolf attacks where there was no direct connection.
IS has directly orchestrated assaults, including the Paris attacks which killed 130 people. This year, the group claimed responsibility for the Easter suicide attacks which killed 269 people in Sri Lanka.
The extremist group has attracted tens of thousands of foreigners to whom it provided advanced military training, and forged affiliate groups in Egypt, Libya, Afghanistan and elsewhere that continue to carry out attacks.
What impact will Baghdadi's death have?
Al-Baghdadi had a $25m bounty placed on his head by the US, making him the world's most wanted terrorist.
He managed to avoid detection from the world's most powerful intelligence services for several years, which increased his mystic among followers.
Baghdadi never publicly designated a successor and many of his most trusted henchman have been killed.
His death could spark infighting among would-be successors, which could further weaken the group.
Is this the end of IS?
The terror cult has survived the death of several leaders and senior commanders and has still been able to attract followers.
Some Sunni Muslims who feel as if they have been oppressed by their governments, as well as foreigners, continue to join the group.
It has powerful affiliates in other countries and the remnants of the original group in both Syria and Iraq.
Perhaps even more worrying are the tens of thousands of IS fighters and supporters detained across the Middle East, including those held by Kurdish fighters in eastern Syria.
The US decision this month to pull out of Syria and abandon its former allies to a Turkish invasion allowed hundreds of IS supporters to escape and raised concerns about the security of other facilities.
It is possible that a future IS leader is wearing a prison jumpsuit, quietly recruiting supporters within concrete walls lined with barbed wire and plotting his next move – just as al-Baghdadi once did.