The Financial Times Stock Exchange 100 Index, also called the FTSE 100 Index, FTSE 100, FTSE, or, informally, the "Footsie", is the United Kingdom's best-known stock market index of the 100 most highly capitalised blue chip companies listed on the London Stock Exchange. Founded in 1984 by the Stock Exchange to better reflect activity on the market, it replaced the Financial Times own FT 30.

London Stock Exchange (LSE) is a stock exchange in the City of London, England, United Kingdom. As of August 2023, the total market value of all companies trading on the LSE stood at $3.18 trillion. Its current premises are situated in Paternoster Square close to St Paul's Cathedral in the City of London. Since 2007, it has been part of the London Stock Exchange Group. The LSE is the most-valued stock exchange in Europe as of 2023. According to the 2020 Office for National Statistics report, approximately 12% of UK-resident individuals reported having investments in stocks and shares. According to the 2020 Financial Conduct Authority (FCA) report, approximately 15% of UK adults reported having investments in stocks and shares.