The speculative bubble that collapsed in England in 1720 around the South Sea Company was the South Sea Bubble.
The South Sea Company received a government charter connected with trade and the conversion of government debt. Its shares rose dramatically as promoters and investors expected enormous commercial profits, although the company's actual trade prospects did not justify the prices.
By late 1720, confidence had broken. Share prices plunged, ruining many investors and causing a political scandal in Britain. Parliament investigated the company's directors and the corruption surrounding the promotion of its shares.
The South Sea Bubble is often grouped with France's Mississippi Bubble, which collapsed in the same year. Neither episode was a modern stock-market crash in the narrow sense, but both are classic early examples of speculative financial bubbles and contagious investor enthusiasm.