Trump, 70, took the oath of office in front of about 800,000 people who braved chilly weather to gather on the National Mall in the center of the capital to celebrate the rank political outsider, who defied all odds to defeat political heavyweight Hillary Clinton in the November polls.
Trump placed his left hand on two bibles, including the historic Abraham Lincoln Bible, recited the oath of office on the steps of the Capitol to become the most powerful man on earth. He was administered the oath of office by Chief Justice John Roberts.
In his maiden address to the nation from the US Capitol, Trump promised his countrymen to rebuild the country to "bring back our dreams" wherein "America First" would be the key to his governance.
He vowed to eradicate "radical Islamic terrorism from the face of the earth" and assured the world that his administration does not want to impose its governance over other countries.
"Together, we will determine the course of America and the world for many, many years to come. We will face challenges, we will confront hardships, but we will get the job done," Trump said in an optimistic and visionary inaugural speech that lasted for over 16 minutes.
In an apparent reference to his election campaign, Trump said for too long, a small group in US capital has reaped the rewards of government while the people have borne the cost.
Washington flourished, but the people did not share in its wealth, he rued.
"Politicians prospered, but the jobs left and the factories closed. The establishment protected itself, but not the citizens of our country. Their victories have not been your victories. Their triumphs have not been your triumphs. And while they celebrated in our nation's capital, there was little to celebrate for struggling families all across our land," Trump said.
"We are transferring power from Washington, D.C., and giving it back to the American people," Trump said, as he vowed to address the ills he sees plaguing the nation, including gun violence, drugs and crime.
"This American carnage stops right here and right now," he asserted in presnece of outgoing President Barack Obama.
"That all changes starting right here and right now because this moment is your moment, it belongs to you," Trump said.
"The time for empty talk is over," he said.
"The time for action" has arrived; he said as he vowed a new "national pride" that will "heal divisions."
In an effort to unite the country, Trump said what truly matters is not which party controls the government, but whether the government is controlled by the people.
"January 20, 2017, will be remembered as the day the people became the rulers of this nation again," he said.
"The forgotten men and women of our country will be forgotten no longer. Everyone is listening to you now. You came by the tens of millions to become part of a historic movement the likes of which the world has never seen before," he told his countrymen.
"We are one nation -- and their pain is our pain. Their dreams are our dreams; and their success will be our success. We share one heart, one home, and one glorious destiny. The oath of office I take today is an oath of allegiance to all Americans," Trump said.
Continuing with one of his election campaign theme, Trump said that for many decades, Americans have enriched foreign industry at the expense of American industry.
"Subsidized the armies of other countries while allowing for the very sad depletion of our military. We have defended other nation’s borders while refusing to defend our own; and spent trillions of dollars overseas while America's infrastructure has fallen into disrepair and decay," he said.
"We have made other countries rich while the wealth, strength, and confidence of our country has disappeared over the horizon. One by one, the factories shuttered and left our shores, with not even a thought about the millions upon millions of American workers left behind," he added.
And the wealth of the middle class has been ripped from their homes and then redistributed across the entire world.
"But that is the past. And now we are looking only to the future. We assembled here today are issuing a new decree to be heard in every city, in every foreign capital, and in every hall of power," Trump said.
"From this day forward, a new vision will govern our land. From this moment on, it’s going to be America First. Every decision on trade, on taxes, on immigration, on foreign affairs, will be made to benefit American workers and American families," he said.
Reiterating his pledge to protect borders from the ravages of other countries making American products, stealing its companies, and destroying jobs, Trump said protection will lead to great prosperity and strength.
"I will fight for you with every breath in my body -- and I will never, ever let you down. America will start winning again, winning like never before," he said.
"We will bring back our jobs. We will bring back our borders. We will bring back our wealth. And we will bring back our dreams," Trump said.
Trump said his administration will follow two simple rules.
"Buy American and hire American," he said amidst applause from the thousands of people gathered at the National Mall to listen to his speech.
"We must think big and dream even bigger. In America, we understand that a nation is only living as long as it is striving. We will no longer accept politicians who are all talk and no action, constantly complaining, but never doing anything about it. The time for empty talk is over. Now arrives the hour of action," he said in the presence of former US presidents Bill Clinton, George W. Bush and Jimmy Carter.
He asked his countrymen to not allow anyone to tell them that it cannot be done.
"No challenge can match the heart and fight and spirit of America. We will not fail. Our country will thrive and prosper again," he asserted.
"We stand at the birth of a new millennium, ready to unlock the mysteries of space, to free the earth from the miseries of disease, and to harness the energies, industries and technologies of tomorrow.
"A new national pride will stir ourselves, lift our sights and heal our divisions," he said.
"Together, we will make America strong again. We will make America wealthy again. We will make America proud again. We will make America safe again. And yes, together we will make America great again," Trump said as he concluded his speech with his election slogan that propelled him to a surprising victory last November.
Earlier, Mike Pence was also sworn-in as US Vice President.