The FTSE 100, or Financial Times Stock Exchange 100 Index, is a stock market index that represents the 100 largest companies listed on the London Stock Exchange by market capitalization. It serves as a key indicator of the UK’s economic health and performance, encompassing major industries such as finance, energy, and consumer goods. The FTSE 100 provides investors and analysts with a snapshot of the market's overall trends and the financial stability of leading British companies.