Stephen Hawking has backed the campaign for Britain to stay in the EU, saying Brexit would be a "disaster for UK science".
The academic leads more than 150 Fellows of the Royal Society in calling for a vote to remain, in a letter to The Times.
Professor Hawking said leaving the EU would severely affect research in the UK as many young scientists were now recruited from Europe.
In the letter, the scientists wrote: "We now recruit many of our best researchers from continental Europe, including younger ones who have obtained EU grants and have chosen to move with them here.
"Being able to attract and fund the most talented Europeans assures the future of British science and also encourages the best scientists elsewhere to come here."
The signatories - including University of Cambridge professor Sir Alan Fersht, who specialises in protein science and organised the letter - also claim that increased funding from the EU has benefited the UK and science as a whole.
In the letter the scientists also note the example of Switzerland, which despite paying in to the EU, has limited access to funds and struggles to attract young talent because of freedom of movement restrictions.
They add: "If the UK leaves the EU and there is a loss of freedom of movement of scientists between the UK and Europe, it will be a disaster for UK science and universities.
"Investment in science is as important for the long-term prosperity and security of the UK as investment in infrastructure projects, farming or manufacturing; and the free movement of scientists is as important for science as free trade is for market economics."