The 1720 British speculative bubble linked to a company trading rights in the South Seas was the South Sea Bubble.
The South Sea Company received a government-backed monopoly over trade with parts of South America in 1711. In practice, its commercial opportunities were much smaller than many investors imagined. The company later proposed converting government debt into its shares, encouraging a dramatic rise in the stock price during 1720.
Speculation spread through Britain, and investors rushed into the South Sea Company and numerous other ventures. Shares climbed rapidly before confidence collapsed. The company’s stock fell from a peak near £1,000 in August 1720 to roughly £100 by December. Parliament investigated the episode, uncovering corruption and improper influence.
The South Sea Bubble is often grouped with John Law’s Mississippi Bubble in France, which also burst in 1720, but they were separate schemes. Neither episode was a modern exchange crash in the same sense as 1929 or 1987. They are important early examples of debt-financed speculation, promotional hype, insider influence, and the danger of treating rising prices as proof of real value.