Sir Richard Branson said the Kingdom of Saudi Arabia will plough around $1 billion (£760 million) into Virgin's string of space companies.
The cash-injection will be made into Virgin Galatic, The Spaceship Company and Virgin Orbit - with the option of $480 million (£364 million) of extra investment.
The Virgin Group founder said it would also open up the possibility of creating a "space-centric" entertainment industry in Saudi Arabia.
In a post on Virgin's website, Sir Richard wrote: "This investment is a sign of confidence from the international investment community that our vision, our approach and our technology are the right path to commercialising space access.
"We are now just months away from Virgin Galactic sending people into space and Virgin Orbit placing satellites around the Earth.
"This investment will enable us to develop the next generation of human spaceflight, more economic satellite launches and accelerate our programme for trans-continental point-to-point space travel."
The investment, which will need US regulatory approval, will see the Public Investment Fund of Saudi Arabia take a significant stake in the three Virgin space companies.
However, Sir Richard said Virgin would remain the majority shareholder and the firms would continue to be based in Southern California and New Mexico.
Saudi Arabia's crown prince Mohammad bin Salman Al-Saud, said: "This partnership with Virgin Group reflects the great strides the kingdom is making towards our vision for a diversified, knowledge-based economy.
"The future of Saudi Arabia is one of innovation, as showcased at this week's Future Investment Initiative, and it's through partnerships with organisations like Virgin Group that we will make active contributions to those sectors and technologies that are driving progress on a global scale."