The 1720 speculative market crisis involving the South Sea Company in Britain was called the South Sea Bubble.
The South Sea Company received a government-backed monopoly over trade with parts of South America, although its actual commercial prospects were far less impressive than the publicity surrounding its shares. In 1720, investors drove the stock price to extraordinary heights as speculation spread through London.
The company’s shares reached about £1,000 in August 1720 before collapsing. Many investors lost fortunes, and the shock damaged public confidence in financial companies and government-sponsored schemes. Parliament investigated the scandal, uncovering corruption and conflicts of interest.
The episode formed part of a wider European speculative boom. France experienced the Mississippi Bubble at roughly the same time, but that was a separate scheme associated with John Law. South Sea Bubble is therefore the specific answer for Britain’s 1720 collapse.