Elon Musk, the world's richest man, planned to spend election night with Donald Trump in Florida at his Mar-a-Lago resort, he said on X/Twitter.
Mr Musk, the owner of Tesla and X, has aggressively campaigned for the Republican candidate in swing states across the country.
Trump's campaign is also hosting a watch party at the Palm Beach Convention Center for thousands of supporters.
The tech billionaire has emerged as one of the most important backers of Trump and donated more than $119m (£91.6m) this election cycle to America PAC - a political action committee he created to support the former president.
Mr Musk announced his support for the former president earlier this year, despite saying in 2022 that "it's time for Trump to hang up his hat and sail into the sunset".
He posted a photo of himself on Tuesday saying he voted in Cameron County, Texas - where some of his companies are headquartered - before heading to Florida.
Later in the evening, he wrote on X, "Game, set and match".
The campaign was feeling confident late on Tuesday as supporters gathered at Trump's headquarters in the Palm Beach convention centre to wait for results. At one point, the crowd broke into a dance celebration to YMCA.
Huge cheers erupted in the crowd as the state of Florida was projected as a win for Trump, albeit a win that was never in doubt.
Former congresswoman Tulsi Gabbard arrived at the party, after previously attending Trump's more exclusive watch party at Mar-a-Lago.
"There's a lot of really excited people there" who were "cautiously optimistic", she told the BBC.
Steve Witkoff, a close friend of Trump, was also with him at Mar-a-Lago. There was "a strong feeling of excitement and purpose", he said.