The 1720 British stock-market bubble that collapsed after speculative trading in government debt was the South Sea Bubble.
The South Sea Company was founded in 1711 and received a monopoly over British trade with Spanish South America, although its actual commercial opportunities were limited. In 1720, the company proposed converting part of the national debt into its shares. Promotion, easy credit, and expectations of enormous profits drove its share price sharply higher.
The price then collapsed later in 1720, ruining many investors and exposing serious corruption and insider dealing. Parliament investigated the affair, and the scandal damaged public confidence in financial speculation. The South Sea Bubble is often mentioned alongside France’s Mississippi Bubble, which burst during the same year, but they were separate schemes. Tulip Mania occurred in the Dutch Republic during the seventeenth century, not in Britain in 1720.