Mr Farage said the “Brexit celebration” will take place in Parliament Square to mark the moment the UK leaves the EU at 11pm.
“It is a big moment in the history of this nation to celebrate,” Brexit Party leader Mr Farage posted on Twitter on Wednesday.
Leave Means Leave, a cross-party campaign group, has also called for Boris Johnson to appear on stage “to mark the extraordinary date”.
Its brexitcelebration.com website had already started inviting people to register their interest before getting permission to hold the event.
The site also features a ticker counting down the seconds until Brexit happens.
On Tuesday, Mr Johnson also floated the prospect of Big Ben “bonging” at the 11pm departure time.
He said it would cost £500,000, but that members of the public may be able to donate money to pay for it.
The prime minister told the BBC: "We're working up a plan so people can bung a bob for a Big Ben bong, because there are some people who want to.
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"Because Big Ben is being refurbished, they seem to have taken the clapper away, so we need to restore the clapper.
"And that is expensive, so we're looking at whether the public can fund it."