Trump arrived in Riyadh after an overnight flight and was welcomed at elaborate airport ceremony punctuated by a military flyover and a handshake from Saudi King Salman.
Trump's visit to Saudi Arabia kicked off his first foreign trip as president.
Trump's trip has been billed by the White House as a chance to visit places sacred to three of the world's major religions, while giving him time to meet with Arab, Israeli and European leaders.
As he arrived, the president waved from the doorway of Air Force One and then descended the steps, joined by first lady Melania Trump.
Trump remains popular in the Gulf, where leaders hope he'll take a harder line on Iran than Obama did.
As Mr Trump and the 81-year-old king, who was aided by a cane, walked along the red carpet, military jets flew swept the sky, leaving a red, white and blue trail.
US first lady Melania Trump is not following local custom about women covering their heads in Saudi Arabia. "Great to be in Riyadh, Saudi Arabia. Looking forward to the afternoon and evening ahead".
Shortly afterward, the pageantry continued inside the Saudi Royal Court, where Salman presented Trump with a gilded necklace and medal, the country's highest honor. British Prime Minister Theresa May and German Chancellor Angela Merkel did not wear head coverings in visits earlier this year.
The king and Trump were overheard discussing natural resources and arms, and the king bemoaned the destruction caused by Syria's civil war.
Jurgen Klopp: Liverpool are already "back on track"
But he insists he can not change his decisions even if Liverpool miss out, adding: "Probably a few will think it's not enough. Ian Wright is backing Liverpool to beat Middlesbrough and secure a place in next season's Champions League competition.
White House officials hope the trip, complete with images of the accompanying pomp and pageantry of a president overseas, will help Trump recalibrate after one of the most hard stretches of his young presidency.
Trump has fueled the Russian Federation controversy by firing the man who was originally leading the Russian Federation probe, FBI Director James Comey, in an apparent bid to stop the investigation.
The question was a harbinger of questions to come for Trump's advisers on their first foreign swing, though Trump himself has not scheduled any news conferences for his entire nine-day trip.
He also told them that firing Mr Comey had "taken off" the "great pressure" he was feeling from the investigation, the Times reported.
On Friday, a report by The Washington Post that the probe into his campaign's Russian Federation ties had identified a "significant person of interest" in the White House undercut Trump's insistence his election bid had nothing to do with the Kremlin.
Despite those troubles, Trump was warmly received in Saudi Arabia in contrast to his predecessor. The king did not greet Obama at the airport as he did Saturday with Trump. Britain's Prince Charles donned traditional robes and a sword as part of his tour of the Middle East in 2014, and former US President George W. Bush in 2008 held a sword and linked arms with King Salman, who was prince at the time.
But her decision is consistent with custom for female foreign dignitaries visiting Saudi Arabia.
"Many people are saying it was wonderful that Mrs. Obama refused to wear a scarf in Saudi Arabia, but they were insulted.We have enuf enemies", Trump said on Twitter in January 2015.
U.S. technology and engineering conglomerate GE said on Saturday it had signed $15 billion of business deals with Saudi Arabia as part of the kingdom's drive to diversify its economy beyond oil.
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