Yemen, the Saudi economy and the Qatar-Gulf crisis will be high on agenda for Mohammed bin Salman
Mohammed bin Salman, named Saudi crown prince on Wednesday, becomes first in line to the throne as the historically conservative nation faces challenges at home and turmoil abroad.
Here are three key areas to watch.
Prince Mohammed retains his position as defence minister, a post he held when Riyadh joined the war in neighbouring Yemen in 2015.
Sunni-ruled Saudi Arabia heads a regional military alliance fighting Shiite Huthi rebels, accused of ties to Iran, for control of the impoverished country.
In May 2017, faced with international criticism over the Saudi-led alliance's role in Yemen's humanitarian crisis, the prince said his country had "no choice" but to intervene in the war to support the Saudi-allied, UN-recognised government of Abedrabbo Mansour Hadi.
"These militias posed a threat to international shipping" in the Red Sea, Mohammed said in a televised interview.
"If we had waited, the threats would grown more complicated, and there would have been a threat to Saudi Arabia".
Mohammed defended Saudi Arabia's decision to fight a long war in Yemen as the sole means to protect civilians in the fight against the Huthis and their allies, former troops loyal to ex-Yemeni president Ali Abdullah Saleh.
"We could eliminate the Huthis and Saleh in a few days ... but as a result thousands of our troops and Yemeni civilians would be the victims," he said.
International rights groups have criticised both sides in the war for human rights violations, accusing the Saudi-led alliance of attacking civilian targets including hospitals and schools.
Human Rights Watch in January said some of those attacks may amount to war crimes.
Amnesty International in March said Saudi arms purchases from the US and Britain were "used to commit gross violations and helped to precipitate a humanitarian catastrophe".
Prince Mohammed is the chief architect of an ambitious plan to transform the Saudi economy by 2030 to reduce its dependence on oil and develop the private sector.
Saudi Arabia, the world's largest exporter of oil, was dealt a serious blow when oil prices plummeted in 2014.
Under the "Vision 2030" plan, unveiled in April 2016, Saudi Arabia will sell nearly five percent of state-owned Aramco -- the world's largest oil company reportedly worth between $2 trillion and $2.5 trillion.
The sale would mark the first move towards Aramco's privatisation.
The plan aims to create a sovereign wealth fund worth $2 trillion, which would make it the largest state-owned investment fund in the world.
It targets an increase in non-oil government revenue sixfold from $43.5 billion to $267 billion.
It aims to raise non-oil exports and boost the contribution of the private sector to gross domestic product (GDP) from 40 percent to 65 percent.
The economic plans are also aimed at bringing about tentative societal change by expanding local industry and slashing unemployment.
Women, who face some of the world's harshest restrictions in Saudi Arabia, are expected to constitute 30 percent of the workforce by 2030, up from 22 percent now.
Prince Mohammed is one of the prime movers behind Saudi Arabia's decision earlier this month to isolate Qatar, accusing the gas-rich emirate of ties to Shiite rival Iran and of facilitating the financing, and function, of extremist groups.
Saudi Arabia has sealed off Qatar's only land border to the outside world and the three Gulf states have banned all flights to and from Doha.