The Tesla CEO, who often sends funny tweets, said on Wednesday, “I’m buying Manchester United ur welcome.”
Just after 01:00 BST on Wednesday, Elon Musk - who is reported to have a net worth of $270bn (£223bn) according to Forbes - posted on Twitter: "Also, I'm buying Manchester United ur welcome."
Cue pandemonium on the social network, with the American's tweet receiving more than 900,000 likes.
But when asked on Twitter if he was being honest, he said: “No, this is a long-running joke on Twitter. I’m not buying any sports teams.”
They are bottom of the Premier League after two defeats, star player Cristiano Ronaldo could leave, while new signings are failing to materialise.
Last year, when United tried to start an independent European Super League but failed, the anti-Glazer campaign picked up speed.
Manchester United is owned by the Glazer family, which also owns the Tampa Bay Buccaneers.
Since 2013, they haven’t won the league, and their fans often protest against the club’s owners. With a value of almost £4 billion, or just under $5 billion, the club is still a major business force.
Some fans welcomed Musk's interest in their club, which was valued at $4.6bn (£3.8bn) by Forbes earlier this year.
Adil Huseynzada, CEO of SKAUT, commented on this matter as follows:
"Actually, we expect a lot from Elon Musk. He may be one of the best entrepreneurs who can bring blockchain solutions to football and build a new team management."