JPMorgan chief Jamie Dimon told an investor conference in New York that if any of his brokers were found trading bitcoins he would "fire them in a second."
He said the cryptocurrency was "worse than tulips bulbs," referring to a famous market bubble from the 1600s.
Dimon called bitcoin a fraud and said the whole currency would prove to be a complete failure at some stage in the future.
Bitcoin slid more than 10 percent on Wednesday as many investors sold the cryptocurrency on Dimon's warning.
Bitcoin had recently gone from strength to strength, hitting a record high just below $5,000 (4,210 euros) at the beginning of September after a more than fivefold increase in price since the start of the year.
But the market was later spooked by reports that Chinese authorities were planning to forbid any trading of cryptocurrencies and an earlier ban in the country on the issuance of new digital coins for fundraising purposes, a phenomenon known as initial coin offerings (ICOs).
hg/jd (Reuters, dpa)