The 1840s British speculative boom and crash centered on railway shares was called Railway Mania.
Railway Mania peaked in Britain around 1845, when investors rushed to finance proposed railway companies. Parliament received thousands of applications for new lines, and promoters presented railways as opportunities for transportation, commerce, and handsome returns. Share prices often rose before projects were built.
The boom weakened as interest rates increased, construction costs rose, and investors became more skeptical about projected profits. Many companies struggled or failed, and railway shares fell sharply. The resulting losses affected investors and contributed to financial pressure in the wider economy.
Railway Mania is sometimes grouped with earlier British speculative episodes such as the South Sea Bubble, but it involved a different technology and a different decade. It also left a lasting physical legacy: many routes approved during the boom became part of Britain's railway network.