SpaceX will fly two people to the moon next year - a feat not attempted since Nasa's Apollo heyday nearly 50 years ago.
The pair, who know each other, have already paid a "significant deposit" to take the week-long trip.
But their identities and exactly how much they have paid will not be publicly revealed, SpaceX founder Elon Musk said.
All he would say was that they were "not from Hollywood" suggesting they are not celebrities.
The space tourists will receive extensive training before the 240,000 mile flight.
Their journey will see them make them a long loop around the moon, skimming its surface and then going up to 400,000 miles further.
However, the mission will not involve a lunar landing.
"This should be a really exciting mission that hopefully gets the world really excited about sending people into deep space again," Musk said.
If successful, it will be the first flight beyond the International Space Station.
A test flight for the Crew Dragon capsule they will travel on - which has not yet flown in space - is scheduled for later this year.
Musk expects to have more moon-mission customers as time goes by.
Just late last week, Nasa announced it was studying the possibility of adding crew to the test flight of its megarocket, at the request of the Trump administration.
But such a flight to the lunar neighborhood wouldn't happen before 2019 at best.
SpaceX is also working on a so-called Red Dragon, meant to fly to Mars around 2020.