Farage, who previously said he would not stand in the election, says he will lead the anti-immigration Reform UK party.
Farage, 60, had previously said he would not stand in the July 4 vote in order to help his friend Donald Trump campaign for the US election later this year.
He said he will run for the anti-immigration party in a Eurosceptic seat in southeast England and also return as the party leader.
“I’ve decided I’ve changed my mind,” Farage told a news conference. “It’s not always a sign of weakness; it could potentially be a sign of strength.”
Reporting from London, where Farage gave a press conference to announce his candidacy, Al Jazeera’s Charlie Angela said Farage’s decision would likely boost Reform UK’s chances in the vote.
“This [Farage’s] press conference was put together so hastily that even some senior members of the Reform party didn’t know it was happening. This proves what a master of political theatrics Nigel Farage is,” she said.
Angela noted that Farage has been campaigning and speaking to young people.
“He says he’s seen the rejection of the political class for the first time in decades,” she said.
Farage has stood unsuccessfully for Parliament seven times but is still one of the most influential British politicians of his generation, putting pressure on a succession of prime ministers to take tougher positions on Europe and immigration.
At the last general election in 2019, Farage’s party decided not to contest seats held by the Conservatives, then led by Boris Johnson, to avoid splitting the pro-Brexit vote.
Polls suggest the opposition Labour Party is on course for victory this time, with the Conservatives staring at one of the worst results in their history.
Support for Reform UK runs at about 10 percent nationally, giving the party the third highest vote share, polls show.
Angela reported that Farage has said that the conservatives were already crushed and he hopes to get votes from Labour voters.
Conservative leader Sunak has already tried to win over voters tempted by Reform with policies such as tax cuts for pensioners and the reintroduction of national service.
Asked on Monday if he was worried about Farage entering the contest, Sunak said a vote for Reform would help the opposition Labour Party win the election.