Organisers say they are protesting against policies imposed by US President Donald Trump, including the war in Iran, federal immigration enforcement and the rising cost of living.
"Trump wants to rule over us as a tyrant. But this is America, and power belongs to the people - not to wannabe kings or their billionaire cronies," organisers said.
A White House spokesperson called the protests "Trump Derangement Therapy Sessions" and said the only people who care "are the reporters who are paid to cover them".
Throughout the day on Saturday, demonstrations took place in nearly every major US city, including New York, Washington DC, Los Angeles, Boston, Nashville and Houston. Crowds also gathered in smaller cities and towns across the country.
Rallies took over the streets of downtown Washington DC throughout the afternoon, with throngs of people marching through the nation's capital. Protesters lined the steps of the the Lincoln Memorial and packed the National Mall.
One of the flagship No Kings protests on Saturday took place in Minnesota, where two American citizens - Renee Nicole Good and Alex Pretti - were killed by federal immigration agents in January. Their deaths sparked outrage and nationwide protests against the Trump administration's immigration tactics.
Thousands on Saturday filled the streets with signs and a plethora of high-profile Democrats also took a stage outside the State Capitol building in St Paul.
Bruce Springsteen also took the stage and performed his anti-immigration enforcement song titled, "Streets of Minneapolis".
Protesters rallied outside the Minnesota State Capitol in Saint Paul, the state that became central to the debate over the Trump administration's immigration tactics after two Americans were shot by federal immigration agents in January.
Thousands also crowded New York City's Times Square, marching through Manhattan's Midtown neighbourhood. Police had to shut down the normally busy streets to make way for crowds. In October, the New York Police Department said more than 100,000 people had gathered across all five of the city's boroughs.
The protests weren't without incident. In Los Angeles, two people were arrested for assaulting federal law enforcement, according to the Department of Homeland Security (DHS).
In a statement to X, it said that two officers had been hit with the cement blocks and were receiving medical care, after a group of what it described as "1,000 rioters" surrounded the Roybal Federal Building and began throwing things at DHS agents.
Police confirmed that federal authorities used "non-lethal measures" to move crowds in the area, after warning protesters not to "attempt to tear down the gate and not throw items".
Reuters reported that arrests were also made in Dallas, after "minor scuffles erupted" when counter-protesters blocked streets and disrupted the No Kings march.American expats abroad also gathered for protests in cities such as Paris, London and Lisbon.
Several US states mobilised the National Guard, but organisers have maintained that the events are peaceful.
Since returning to the White House in January 2025, Trump has expanded the scope of presidential power, using executive orders to dismantle parts of the federal government and deploying National Guard troops to US cities despite objections by state governors.
A crowd made up of American expats and some French nationals protest in Paris' Place de la Bastille
The president has also called on the administration's top law enforcement officials to prosecute his perceived political enemies.
The president says his actions are necessary to rebuild a country in crisis and has dismissed accusations that he is a behaving like a dictator as hysterical. "They're referring to me as a king. I'm not a king," he said in an interview with Fox News in October.
But critics warn some of the moves by his administration are unconstitutional and a threat to American democracy.