Permission for the 20ft (6m) high inflatable, dubbed “Trump Baby”, to rise above Parliament Square Gardens for two hours on the morning of Friday July 13 has been granted to protesters by the Greater London Authority.
Mr Trump is expected to arrive in the capital the evening before the planned stunt and is likely to visit Blenheim Palace, meet the Queen at Windsor, hold talks with Prime Minister Theresa May at Chequers, and travel to his golf courses in Scotland during the trip.
London Mayor Sadiq Khan and the American leader have engaged in a long-running war of words over issues like crime and terrorism.
Activist Leo Murray said: “We didn’t get off to the best start with the Mayor’s office over this, who originally told us that they didn’t recognise Trump Baby as legitimate protest.
“But, following a huge groundswell of public support for our plan, it looks like City Hall has rediscovered its sense of humour. Trump Baby will fly.”
A spokesman for the Nona Hurkmans group, which is behind the protest, said: “We are just a small group of friends who set out to use humour to take a stand against the rise of racist and fascist politics both here in the UK and over in the US.
“We have been genuinely overwhelmed and touched by the incredible levels of support we have received for our project.”
More than 10,000 people signed a petition calling for the inflatable to be given permission to fly, activists said.