UPDATE: SEE WSJ Reporting of $200 Million Investment in Bitcoin Not True.

Joe Lewis, a billionaire foreign-exchange trader who teamed up with hedge-fund manager George Soros in 1992 to bet against the Bank of England, is the latest high-profile financier to throw his weight behind the virtual currency called bitcoin.

Mr. Lewis leads the Phoenix Fund, a Zurich-based private-equity fund that on Tuesday plans to invest $200 million in Avalon, a company that makes computer servers aimed at creating bitcoins, according to people familiar with the situation.

Bitcoin is a virtual currency that exists online and isn’t backed by any government or central bank. Bitcoins were invented in 2008 by a computer programmer who goes by the pseudonym Satoshi Nakamoto, who describes it as a peer-to-peer electronic cash system.