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.

A stock exchange, securities exchange, or bourse is an exchange where stockbrokers and traders can buy and sell securities, such as shares of stock, bonds and other financial instruments. Stock exchanges may also provide facilities for the issue and redemption of such securities and instruments and capital events including the payment of income and dividends. Securities traded on a stock exchange include stock issued by listed companies, unit trusts, derivatives, pooled investment products and bonds. Stock exchanges often function as "continuous auction" markets with buyers and sellers consummating transactions via open outcry at a central location such as the floor of the exchange or by using an electronic trading platform.