He departs Trump Tower, his Manhattan home and campaign headquarters, for New York's La Guardia airport where he will board an aircraft from the presidential fleet.
The Republican billionaire launched the day with a short burst of his trademark tweets:
"The journey begins and I will be working and fighting very hard to make it a great journey for the American people. I have no doubt that we will, together, MAKE AMERICA GREAT AGAIN!"
He departs Trump Tower, his Manhattan home and campaign headquarters, for New York's La Guardia airport where he will board an aircraft from the presidential fleet, leaving behind his private Boeing jet.
With President Barack Obama's departure on Friday, Trump becomes Air Force One's most exclusive passenger.
The Republican will place a wreath at Arlington National Cemetery at 3:30 pm (2030 GMT) and then will cross the Potomac to speak at the Lincoln Memorial, the epicenter of the inaugural festivities complete with country music concerts and fireworks.
Trump's swearing-in, on the steps of the Capitol at noon Friday -- a date and hour set by the US Constitution -- will be carried live on screens throughout the planet. Rain is forecast.
Hundreds of thousands of citizens, Trump supporters and protesters, have begun converging on the capital for the democratic ritual. Numerous dignitaries, including his unsuccessful Democratic rival for the presidency, Hillary Clinton, and three former presidents will be in attendance.
Trump is "very anxious to get to the White House and get to work for the American people," said his vice president, Mike Pence, a 57-year-old Christian conservative from Indiana.
For new American leaders, the tone, style and agenda of their presidencies are often set from their arrival in Washington through their first few days in office.
Trump, 70, a real estate magnate with no previous political or military experience, was elected in part for his abrasiveness: his working class supporters have sent him to this bastion of federal power to turn the page on the Obama era and dynamite the political status quo. Trump has vowed to act, and swiftly.
After showing Obama the door on Friday, Trump is expected to sign four or five decrees on Friday and then a raft of others beginning Monday to dismantle every policy he can without awaiting congressional approval: immigration, environment, energy, labor regulations.
He still has to finish writing his inaugural address, which he delivers on Friday. In December, at his private Mar-a-Lago estate in Florida, he confided that he sought inspiration from John F. Kennedy and Ronald Reagan.
Kennedy devoted his 1961 inaugural address to the state of the world in the midst of the Cold War, famously appealing to his countrymen: "Ask not what your country can do for you, ask what you can do for your country."
Reagan, in 1981, declared: "The government is not the solution to our problem; government is the problem."
Trump has consulted some historians, read the speeches of his predecessors and sought help writing the address from his closest advisers.
But his spokesman Sean Spicer says the words will be Trump's own.
"It will be very visionary and lay out where he wants to take his country," Spicer added.
It will last about 20 minutes, the same as Obama's first inaugural in 2009, he said.
The 55-year-old outgoing president laid down a clear warning to his successor on Wednesday. While he did not intend to get involved in day-to-day politics, he would not remain silent if certain red lines were crossed, Obama said.
"I put in that category if I saw systematic discrimination being ratified in some fashion. I put in that category explicit or functional obstacles to people being able to vote, to exercise their franchise. I'd put in that category institutional efforts to silence dissent or the press," he said.
"And for me at least, I would put in that category efforts to round up kids who have grown up here and for all practical purposes are American kids, and send them someplace else, when they love this country."
The Democratic opposition is organizing without Obama.
A third of the Democrats in the House of Representatives will boycott Friday's ceremony. And in the Senate, Democrats are putting obstacles in the path of Trump's cabinet nominees, only a handful of whom look to be confirmed Friday, although Republicans had hoped to confirm seven on the new administration's first day.