A cryptocurrency bubble is a phenomenon where the market increasingly considers the going price of cryptocurrency assets to be inflated against their hypothetical value. The history of cryptocurrency has been marked by several speculative bubbles on a boom to bust cycle.

Some economists and prominent investors have expressed the view that the entire cryptocurrency market constitutes a speculative bubble. Adherents of this view include Berkshire Hathaway board member Warren Buffett and several laureates of the Nobel Memorial Prize in Economic Sciences, central bankers, and investors.

In February 2011, the price of Bitcoin rose to US$1.06, then fell to US$0.67 that April. This spike was encouraged by several Slashdot posts about it. In June 2011, Bitcoin's price again rose, to US$29.58. This came after attention from a Gawker article about the dark web market Silk Road. The price then fell to US$2.14 that November.

In November 2013, Bitcoin's price rose to US$1,127.45. It then gradually declined, bottoming out at US$172.15 in January 2015.

The 2018 cryptocurrency crash (also known as the Bitcoin crash and the Great crypto crash) was the sell-off of most cryptocurrencies starting in January 2018. Long Blockchain Corp. is considered a vivid example and textbook example of market euphoria during the 2017 bubble. After an unprecedented boom in 2017, the price of Bitcoin fell by about 65% from 6 January to 6 February 2018. Subsequently, nearly all other cryptocurrencies followed Bitcoin's crash.

By September 2018, cryptocurrencies collapsed 80% from their peak in January 2018, making the 2018 cryptocurrency crash worse than the dot-com bubble's 78% collapse. By 26 November, Bitcoin also fell by 80% from its peak, having lost almost one-third of its value in the previous week.

A January 2018 article by CBS cautioned about possible fraud, citing the case of BitConnect, a British company which received a cease-and-desist order from the Texas State Securities Board. BitConnect had promised very high monthly returns but had not registered with state securities regulators or given their office address.

In November 2018, the total current value for Bitcoin fell below $100 billion for the first time since October 2017, and the price of Bitcoin fell below $4,000, representing an 80 percent decline from its peak the previous January. Bitcoin reached a low of around $3,100 in December 2018.

Wired noted in 2017 that the bubble in initial coin offerings (ICOs) was about to burst. Some investors bought ICOs in hopes of participating in the financial gains similar to those enjoyed by early Bitcoin or Ethereum speculators.

In June 2018, Ella Zhang of Binance Labs, a division of the cryptocurrency exchange Binance, stated that she was hoping to see the bubble in ICOs collapse. She promised to help "fight scams and shit coins".