It will be a working visit, which will see him have meetings with the Prime Minister, British business leaders and the Queen.
The president was delayed for nearly an hour when the North Atlantic Treaty Organisation summit in Brussels he had been attending overran because he demanded member states increase their contributions faster than originally planned.
Trump's visit to the United Kingdom, the 12th US President to make such a tour, comes amid what he described as "turmoil" for the United Kingdom government, as Prime Minister May faces down a rebellion from within her own party over her Brexit strategy.
The trip includes meetings with Prime Minister Theresa May, who has described the United States as Britain's strongest ally, and is determined to secure a trade deal after the country acts on Brexit and leaves the European Union in March 2019.
May's future was thrown into question after two high-level cabinet members -including Foreign Secretary Boris Johnson- resigned amid the growing chaos surrounding Brexit negotiations.
"I've always liked writing amusing songs and he just lends himself to them". The people voted to break it up so I would imagine that's what they would do, but maybe they're taking a different route - I don't know if that is what they voted for'.
Britain "is in somewhat turmoil", Trump said before departing Washington, remarking that dealing with Putin might surprisingly be the easiest part of the European trip.
But protests against Mr Trump have already started, with about a dozen activists from Stand Up to Racism Scotland staging a brief demo outside the Turnberry course on Wednesday.
One Facebook page advertising a London protest against Trump's first visit to Britain as president has around 60,000 people saying they will attend.
Security is still a cornerstone of the relationship, as are trade and less tangible things like shared language and the fact that many Americans are proud of their British roots.
Tens of thousands of people are expected to protest against Trump's visit in central London on Friday, citing his alleged Islamophobia, controversial policies and "incendiary rhetoric" towards people with disabilities and the LGBTQ community.
Americans in London have been warned to "keep a low profile" during the trip, while a crowd-funded "Trump Baby" blimp has been cleared for take-off on Friday morning outside Parliament House.
A campaign is also underway to get "American Idiot", a 2004 song by the U.S. punk rock band Green Day, to the top of the UK Singles Chart.