BY THE BBC,WASHINGTON DC, 20TH JAN,2017-Donald Trump has taken the oath and now becomes the 45th US president of the United States.
President Trump was sworn in by Chief Justice John Roberts on the steps of the US Capitol in Washington.
Thousands of Trump supporters who travelled across the country lined the streets to witness the occasion.
The moment marks the end of an improbable journey for the property tycoon after a campaign marked by controversy.
In his inaugural address, he promised to be the voice of the “forgotten people”, ignored by Washington politicians.
Today, he said, was “the day the people became rulers of this nation again”.
“I will fight for you with every breath left in my body and I will never ever let you down,” said President Trump.
“America will start winning again, winning like never before.”We will bring back our jobs, bring back our borders, bring back our wealth and we will bring back our dreams.”
Hillary Clinton, who lost to Mr Trump in a dramatic upset in November’s election, was in attendance with her husband, former President Bill Clinton.
President Barack Obama shook hands with each member of the Trump family before the ceremony.
Former presidents and first ladies, including George W Bush and his wife Laura as well as Jimmy Carter, were in attendance.
“I’m here today to honour our democracy & its enduring values. I will never stop believing in our country & its future. #Inauguration”, Mrs Clinton tweeted after her arrival.
The only absences were 92-year-old George Bush Senior, who is in hospital being treated for respiratory problems, and his wife Barbara.
Members of Congress were also in attendance, although more than 50 House Democrats had refused to attend the ceremony.
The 45th president has vowed to roll back many of his predecessor’s policies, including repealing Mr Obama’s signature health care law and building a wall along the US-Mexico border.
Earlier, about 150 protesters dressed in black marched through Washington, smashing windows and rolling rubbish bins into the street to form blockades.
Thousands of police have been deployed and many kilometres of crowd barriers set up as part of a vast security operation ahead of the inauguration.
Some spectators have waited for hours.
“I’m here for history,” said 24-year-old Kevin Puchalski. “This is the first president that I voted for that won.”
Chris Lehmann, a 55-year-old maintenance supervisor from Belmar, New Jersey, said: “I’m so excited, I’m like, on top of the world.”