Who will be Iran's next supreme leader? One name stands out.

The assassination of Iran's Supreme Leader Ayatollah Ali Khamenei in the early hours of the U.S. and Israel's war on Iran has raised a simple but enormously consequential question: Who will replace him?

For nearly four decades, Khamenei sat atop Iran's complex power structure, serving not just as the country's highest religious authority but also as its ultimate political decision-maker. His killing at the sprawling complex that housed his offices and residence in Tehran has created a vacuum in a system designed above all to prevent exactly that kind of instability.

Formally, the decision now rests with Iran's Assembly of Experts, the powerful clerical body tasked with selecting the country's supreme leader. In practice, however, the outcome will almost certainly emerge from a much smaller circle: senior clerics, the Islamic Revolutionary Guard Corps and the security establishment that has long underpinned the Islamic Republic's power structure.

Several names have already surfaced. But one stands out.

Mojtaba Khamenei

The leading contender is Mojtaba Khamenei, the late leader's second son.

Unlike many figures in Iran's hierarchy, Mojtaba Khameini has never held elected office. But for years he has operated quietly behind the scenes from within his father's office, cultivating influence across the security establishment, particularly within the Islamic Revolutionary Guard Corps.

He studied theology in Qom and fought as a young volunteer during the Iran-Iraq war in the 1980s, credentials that still carry weight within the revolutionary elite. Yet his authority has largely come from proximity to power rather than his religious stature.

He is believed to have deep relationships with senior figures in the Revolutionary Guard. That matters enormously in Iran's political system, where the Guards wield vast military, economic and political power.

Georgetown University professor and Iran expert Mehran Kamrava, in Doha, said a Mojtaba succession would likely reflect the system's instinct for survival.

"The deep state in the Islamic Republic wants continuity," Kamrava said in an interview. "If Mojtaba indeed is chosen as his father's successor, it would indicate more than anything else that the Islamic Republic is trying to ensure continuity."

During Ali Khamenei's tenure, the supreme leader managed to maintain authority over the Revolutionary Guard despite the organization's enormous power inside the state.

Kamrava believes Mojtaba is seen inside Iran's power structure as someone capable of preserving that balance.

"The assumption inside Iran is that Mojtaba has a similarly superior position in relation to the commanders of the Revolutionary Guards," Kamrava said. 

If he is ultimately selected, it would signal that Iran's ruling elite has chosen stability over experimentation at a moment of extreme pressure.

It would also mark something unprecedented in the Islamic Republic: a leadership transition that effectively keeps power within the same family.

And while Mojtaba may be the frontrunner, he is not the only figure under discussion.

Ali Reza Arafi

Another prominent name is Ayatollah Alireza Arafi, a senior cleric deeply embedded within Iran's religious institutions. Arafi serves on both the Guardian Council and the Assembly of Experts and has spent years overseeing Iran's influential network of seminaries in Qom.

Following Khamenei's assassination, Arafi was reportedly elevated to a temporary leadership council tasked with guiding the country during wartime and through the succession process.

Sadeq Larijani

Anther potential candidate is Ayatollah Sadeq Larijani, a former judiciary chief and member of one of Iran's most powerful political families. Larijani has long been viewed as a plausible successor because of his clerical credentials and deep ties to the country's political establishment.

Hasan Khomeini

Some analysts have also pointed to Hassan Khomeini, the grandson of Islamic Republic founder Ayatollah Ruhollah Khomeini. Among clerics and reformist circles he commands respect, though his relatively moderate reputation could make him a difficult choice for Iran's hardline establishment.

Mohammad Mehdi Mirbagheri 

Hardline cleric Mohammad Mehdi Mirbagheri has also been floated as a possible contender due to his ideological alignment with the most conservative factions within Iran's political system.

Unprecedented challenges ahead

Whoever emerges as the next supreme leader, the circumstances surrounding this leadership transition are unprecedented.

Khamenei was killed during the opening phase of a war that has already expanded beyond Iran's borders, with missile and drone attacks rippling across the Gulf and the broader Middle East.

Several senior Iranian officials were also reportedly killed in the early strikes, eliminating potential successors and further narrowing the field of candidates.

President Trump, meanwhile, said Iranian officials who are working on selecting the next supreme leader are "wasting their time."

"Khamenei's son is a lightweight. I have to be involved in the appointment, like with Delcy [Rodriguez] in Venezuela," Mr. Trump said, referring to the interim president who took power after the U.S. captured Nicolás Maduro.

Leadership transitions inside the Islamic Republic are normally carefully choreographed affairs. The last one occurred in 1989 after the death of Ayatollah Ruhollah Khomeini and involved intense negotiations among clerical and political elites before Khamenei ultimately emerged as the compromise choice.

This time the process is unfolding in the middle of an active war.

Kamrava believes another factor shaping Iran's future leadership is generational change inside the Revolutionary Guard.

Many of the commanders who defined Iran's military posture for decades were veterans of the Iran-Iraq war. That experience, he said, often made them more pragmatic.

"The commanders of the Revolutionary Guards who were killed were those who had cut their teeth in the Iran-Iraq war," Kamrava said. "They had seen battle close up and they had moderated."

Their replacements, however, represent a different generation.

"The younger generation… are far more radical, far less pragmatic," Kamrava added. 

That shift may ultimately shape Iran's direction more than the identity of the next supreme leader. 

Despite the shock of Khamenei's assassination, few analysts expect Iran's political system to transform overnight. Kamrava was direct when asked whether a leadership transition might bring significant change.

"I don't think we're going to see radical shifts in the way the Islamic Republic conducts itself," he said. 

The system may adjust tactically. In the past, Iranian leaders have loosened certain social restrictions after major crises to ease domestic pressure.

But strategically, the structure of power inside Iran remains intact. Clerics, Revolutionary Guard commanders and security institutions still dominate the state. And their priority, especially in wartime, is stability.

Whoever emerges as Iran's next supreme leader will inherit a country under immense strain: a widening regional war, a battered economy and a population that has repeatedly taken to the streets in protest over the past decade.

The Islamic Republic has survived crises before. But this moment is different. For the first time since the 1979 revolution, Iran's supreme leader has been killed during a war — and the system he helped shape is now being tested in real time.