Trump and Salman were expected to oversee the signing of multiple agreements between American and Saudi companies on Saturday afternoon, including between the Saudi oil giant Aramco and various US firms.
Trump is embarking upon his first international trip at a moment of deep uncertainty for his young presidency. This week, the Justice Department named a special counsel to investigate Russian meddling in last year's election, including potential ties between Trump associates and Russian officials.
Trump has fueled the Russia controversy by firing the man who was originally leading the Russia probe, FBI Director James Comey, in an apparent bid to stop the investigation. He's also accused of revealing high classified intelligence to Russian officials during an Oval Office meeting last week.
White House aides had hoped Trump's ambitious foreign swing would provide relief from a barrage of bad headlines. But it's increasingly clear that the swirl of controversy will shadow Trump during his stops in Saudi Arabia, Israel, Rome, Brussels, and Sicily.
That hasn't dampened expectations for Trump's arrival in the Arab Gulf, however.
In Riyadh, Saudis were preparing to welcome Trump in grand fashion. A five story image of Trump's face was projected on the exterior of the Ritz Carlton hotel where he'll stay, and large billboards of Trump and King Salman lined the highway from the airport.
Saturday will be the first night Trump sleeps in a property that isn't his own since becoming President. He's slept only at the White House, Mar-a-Lago, and his golf club in Bedminster, New Jersey, since January.
Iran high on the agenda
Trump remains popular in the Gulf, where leaders hope he'll take a harder line on Iran than his predecessor Barack Obama. The US President's visit comes as Iran's President Hassan Rouhani handily won re-election in what is a victory for the Shiite nation's reformist camp.
Saudi Arabia was opposed to the deal the Obama administration helped strike with Iran to curtail its nuclear program. While Trump campaigned as a strident opponent of the nuclear deal, his administration is still reviewing whether or not to scrap the accord.
Leaders in the Gulf are also eager to hear Trump's plan for combating what they regard as Iran's destabilizing presence in Iraq, Syria, and Yemen.
During meetings this weekend, Trump will work to develop relationships with the leaders, with whom the US hopes to partner on fighting extremism.
He's also expected to announce a series of new agreements with the kingdom, including a $100 million arms deal that was brokered primarily by Trump's son-in-law Jared Kushner. The agreement will provide tanks, ships, and missile defense systems to the kingdom in an attempt to bolster its regional military prowess.
Kushner, along with wife Ivanka Trump, were among a large group of aides who traveled with Trump to Saudi Arabia. Trump's staff has become beleaguered in the wake of the Russia headlines, with Trump contemplating large-scale changes to his team.
Why the Muslim-majority nation
Also joining the President: first lady Melania Trump, who disembarked Air Force One alongside her husband Saturday in a flowing black jumpsuit with a gold belt. Like past US first ladies visiting Saudi Arabia, Mrs. Trump's hair was not covered in the local custom, and she shook Salman's hand upon arriving in the kingdom.
When women visit Saudi Arabia from Western nations they typically forgo a head covering. First Lady Michelle Obama followed that practice when accompanying her husband to King Abdullah's funeral in 2015.
Back then, Trump issued sharp criticism of Mrs. Obama, writing on Twitter that she'd "insulted" Saudi citizens.
On Saturday, however, none of the women in Trump's delegation covered their hair, and there appeared to be little consternation from the large delegation of Saudi men who greeted them at the airport.
Trump is the first US president to choose a Muslim-majority nation for his first stop abroad, and his aides have said the decision was meant to rebut notions that Trump is anti-Muslim.
Trump will deliver a major speech Sunday to the leaders of more than two dozen Muslim nations where he'll urge countries to drive out extremists. An early draft of his speech does not contain the phrase "radical Islamic terror," a term which Trump has emphasized back home.
Trump's spokesman Sean Spicer said the President edited the speech with his aides during the 14-hour journey from Washington.
He spent the remainder of the time reading newspapers and getting very little sleep, according to an aide.