What you need to know:
- The hard-charging heir drew international revulsion after Saudi agents killed and dismembered journalist Jamal Khashoggi in 2018, but US President Joe Biden's visit to the kingdom this week looks set to restore his position on the international stage, forcing world leaders to deal with him whether they want to or not.
Saudi Crown Prince Mohammed bin Salman has shaken up the conservative kingdom with head-spinning reforms while quashing any threats to his status since becoming de facto ruler of the world's biggest oil producer five years ago.
The hard-charging heir drew international revulsion after Saudi agents killed and dismembered journalist Jamal Khashoggi in 2018, but US President Joe Biden's visit to the kingdom this week looks set to restore his position on the international stage, forcing world leaders to deal with him whether they want to or not.
A towering figure with a full-face beard, deep growling voice and seemingly boundless energy, Prince Mohammed is known for his super-sized ambitions, from building the futuristic megacity known as NEOM to waging the seven-year-old war in neighbouring Yemen.
The brash 36-year-old, known widely as "MBS" and said to have a fondness for fast food and the "Call of Duty" video games, is also fabulously rich, owning a $500 million yacht, a French chateau and, according to officially denied reports, a $450 million Leonardo da Vinci painting.
Unlike other Saudi princes with their British accents, sharp suits and Oxford degrees, MBS embraces the country's Bedouin roots, usually donning a traditional robe and sandals, treating friends and relatives to lavish roast lamb meals in luxury desert camps.
Having plotted his path to power from relative obscurity, Prince Mohammed has overseen the biggest transformation in Saudi Arabia's modern history, the world's top crude oil exporter and host of Islam's two holiest sites, Mecca and Medina.
Under his rule, the kingdom's religious police have been de-fanged, cinemas have reopened, foreign tourists have been welcomed, and Saudi Arabia has staged a film festival, operas, Formula One Grand Prix, heavyweight boxing, professional wrestling and a huge rave festival.
Yet he has also jailed critics and, in a sweeping purge of the nation's elite, detained and threatened some 200 princes and businessmen in Riyadh's Ritz-Carlton hotel in a 2017 anti-corruption crackdown that tightened his grip on power.
His image was most severely tarnished by the brutal murder of Khashoggi inside the kingdom's Istanbul consulate in October 2018, which prompted condemnation of the crown prince, despite Riyadh's insistence that rogue agents carried out the killing.
"MBS is a hugely divisive character, praised by supporters as a long-awaited game-changer in a region aching for it and dismissed by foes as a brutal dictator in the making," wrote Ben Hubbard in "MBS: The Rise to Power of Mohammed bin Salman".
"He is determined to give Saudis a shining, prosperous future and exercises an unflinching willingness to crush his foes. Combined in different doses, those attributes will likely guide his actions far into the future."
Prince Mohammed, son of King Salman bin Abdulaziz Al Saud, was born on August 31, 1985. He is one of the hundreds of grandchildren of the country's founder, King Abdulaziz Ibn Saud, and grew up in a Riyadh palace with his mother, Fahda, one of his father's four wives, and his five brothers.
"As the sixth son of the 25th son of the founding king, there was little reason to expect that he would rise to prominence," wrote Hubbard. "And for most of his life, few people did."
He earned a law degree from Riyadh's King Saud University but never studied abroad, and soon worked as a special adviser to his father, the then-Riyadh governor.
When King Salman assumed the throne in early 2015, he named Prince Mohammed as defence minister. Soon the young man also coordinated economic policy, oversaw the state oil company Saudi Aramco and supervised the kingdom's military intervention in Yemen.
Within a year, he held so many portfolios that diplomats called him "Mr Everything".
The prince -- now a father of three boys and two girls, who unlike other Saudi royals has only one wife -- reportedly worked 16-hour days and drew inspiration from Winston Churchill and Sun Tzu's "The Art of War".
His rise was rapid, replacing his elder cousin Prince Mohammed bin Nayef to become heir to the throne in 2017. Three years later Prince Nayef, along with a brother of King Salman, was reportedly detained.
Prince Mohammed has pledged to forge a "moderate" Saudi Arabia and courts international investors for his wide-ranging Vision 2030 plan to diversify the oil-reliant economy.
"We want to live a normal life," he once told business leaders in Riyadh. "All we are doing is going back to what we were -- a moderate Islam that is open to all religions and open to the world.
"Seventy percent of the Saudi population is under 30 and, honestly, we will not spend the next 30 years of our lives dealing with extremist ideas. We will destroy them today."
'Fire hose of ideas'
As he rose to prominence, he toured the United States and charmed leaders in the White House and on Wall Street, in Silicon Valley and Hollywood.
New York Times writer Thomas Friedman recounted how in an interview that lasted late into the night, the prince "wore me out with a fire hose of new ideas for transforming his country".
Perhaps his most hyper-ambitious initiative is the $500 billion NEOM project on the Red Sea coast, to be powered by solar energy and staffed by robots, which the prince describes as a "civilisational leap for humanity".
Reflecting the hopes of the country's youthful population, Prince Mohammed has eased restrictions on women's rights, allowing them to drive, attend sports events and concerts alongside men, and obtain passports without the approval of a male guardian.
Along with the reforms, though, came a crackdown on dissidents, including intellectuals and women's rights activists, part of an apparent strategy to stamp out any trace of opposition before a formal transfer of power from King Salman.
Internationally, he has pursued a more assertive foreign policy, plunging the kingdom into a quagmire of regional rivalries: the Yemen war, hostility toward Shiite power Iran, a three-year blockade of Qatar until 2021, and the reported detention of Lebanon's prime minister for several tense days.
Prince Mohammed, who once publicly berated US president Barack Obama for criticising Saudi Arabia's rights record, forged a strong bond with Donald Trump and especially his son-in-law, Jared Kushner, which served him well during the fallout over Khashoggi's death.
The prince initially faced renewed scrutiny of his human rights record from Biden, who released an intelligence report stating MBS had "approved an operation" to capture or kill Khashoggi.
Biden did not, however, take action against the crown prince and this week the pair will meet on Saudi soil, despite an earlier pledge to make the country a "pariah".
This shift is perhaps an acknowledgement that Prince Mohammed, still in his 30s, could rule Saudi Arabia for half a century or more.