Thousands of the president’s backers rallied in the capital on Saturday to protest what they claimed was a stolen election. Mr Trump has repeatedly asserted, without providing firm evidence, that November’s presidential election was rigged against him.
Counter-protestors also gathered, some dressed all in black and carrying shields.
The Trump supporters included several hundred Proud Boys, members of a group accused of far-right sympathies, some of whom wore helmets and body armour.
Video posted on social media showed numerous violent clashes between the two sides, with police attempting to keep the peace.
One clip shows a large firework being thrown at a group of Trump supporters who are being protected by police.
In another a Trump supporting couple are surrounded by counter-protestors with one being punched several times.
Several videos show brawls between Trump backers, many wearing Proud Boys gear, and counter-protestors with batons and bear spray being deployed by both sides.
Separately one person was shot when Trump supporters and opponents clashed in Olympia, capital of Washington state.
Speaking to the Seattle Times Chris Loftis, a spokesman for Washington State Patrol, confirmed two people have detained in connection to the shooting.
He claimed there was a “fluid situation with two groups of size, both including heavily armed individuals”.
Mr Loftis added: “No information confirmed on victim or any injury status.”
President Trump backed the Washington DC protest tweeting: “Wow! Thousands of people forming in Washington (D.C.) for Stop the Steal.
“Didn’t know about this, but I’ll be seeing them!”
On Friday the US Supreme Court rejected a bid to overturn the presidential outcome result by changing the result in four battleground states.