The speculative bubble that burst in England in 1720 was the South Sea Bubble.
The South Sea Company received a government-backed monopoly over trade with Spanish South America, although its practical trading opportunities were limited. Investors were attracted by promotional claims, political connections, and the prospect of converting government debt into company shares.
Shares rose dramatically during the first half of 1720. The excitement spread beyond the company, encouraging speculation in many other ventures. Parliament passed the Bubble Act, partly to restrict competing joint-stock companies, but confidence collapsed later that year. South Sea shares fell sharply, ruining many investors.
The crash is often confused with France’s Mississippi Bubble, which collapsed in the same period under John Law’s financial system. The South Sea episode became a lasting example of speculative excess, misleading promotion, and the danger of buying assets mainly because prices are rising.