British MPs are also holding an emergency debate on Trump's hastily implemented executive order.
In London, Whitehall was turned into a sea of placards as thousands gathered opposite the gates of Downing Street.
High-profile speakers such as former Labor leader Ed Miliband and pop star Lily Allen are expected to address the demonstration, the Independent reported.
Britain’s Shadow attorney general Shami Chakrabarti told the crowd: "It is in sadness and solidarity that we gather here this evening.
"I also hope, friends, that we stand here in solidarity with all the world's women who the president has insulted and all the desperate refugees that he would spurn."
"Today we say with defiance, with determination, we will not stay silent," Jones said.
Similar protests were planned in cities across the UK, including Edinburgh, Cardiff, Leeds, Manchester and Birmingham.
The action follows a petition calling for the US President's UK state visit to be cancelled surged to more than a million signatures after his executive order.
Earlier on Monday, British Foreign Secretary Boris Johnson sought to restore calm by telling Parliament the ban would make "no difference" to British passport holders.
Chants, including "Donald Trump has got to go" and "shame on May" rippled up the swelling crowds on Whitehall.