Major United Kingdom stock market indices

United Kingdom company law regulates corporations formed under the Companies Act 2006. Also governed by the Insolvency Act 1986, the UK Corporate Governance Code, European Union Directives and court cases, the company is the primary legal vehicle to organise and run business. Tracing their modern history to the late Industrial Revolution, public companies now employ more people and generate more of wealth in the United Kingdom economy than any other form of organisation. The United Kingdom was the first country to draft modern corporation statutes, where through a simple registration procedure any investors could incorporate, limit liability to their commercial creditors in the event of business insolvency, and where management was delegated to a centralised board of directors. An influential model within Europe, the Commonwealth and as an international standard setter, UK law has always given people broad freedom to design the internal company rules, so long as the mandatory minimum rights of investors under its legislation are complied with.

The FTSE Fledgling Index comprises companies listed on the main market of the London Stock Exchange (LSE) which qualify as eligible for inclusion in the FTSE UK series but are too small to be included in the FTSE All-Share Index. There is no liquidity requirement for constituents of the FTSE Fledgling Index.

The FT 30 (FT Ordinary Index or FTOI, not "FTSE 30") is a now rarely used index that is similar to the Dow Jones Industrial Average. As an index of stocks to represent the real trends on the market, the FT 30 has been superseded by the FTSE 100, which was introduced in 1984.

The FTSE SmallCap Index is an index of small market capitalisation companies consisting of the 351st to the 619th largest-listed companies on the London Stock Exchange main market. The index, which is maintained by FTSE Russell, a subsidiary of the London Stock Exchange Group, is a constituent of the FTSE All-Share Index which is an index of all 620 companies listed on the main market of the LSE.

The FTSE Global Equity Index Series is a series of stock market indices provided by FTSE Group. It was launched in September 2003, and provides coverage of over 17,000 stocks in 48 countries, covering 98% of the world's investable market capitalization.

The FTSE 250 Index, also called the FTSE 250, or, informally, the "Footsie 250" is a stock market index that measures the real strength of the economy of the United Kingdom and consists of the 101st to the 350th mid-cap blue chip companies listed on the London Stock Exchange.

The London Stock Exchange (LSE) is a stock exchange based in London, England. 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. Since 2007, it has been part of the London Stock Exchange Group (LSEG, which the exchange also lists (ticker symbol LSEG)). Despite a post-Brexit exodus of stock listings from the London Stock Exchange, the LSE was 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 a 2020 Financial Conduct Authority report, approximately 15% of British adults reported having investments in stocks and shares.

The FTSE All-Share Index, originally known as the FTSE Actuaries All Share Index, is a capitalisation-weighted index, comprising around 600 of more than 2,000 companies traded on the London Stock Exchange (LSE). By weighting companies based on their market capitalisation, the index ensures that companies with larger market capitalisations have a greater influence on the index's performance. Since 29 December 2017 the constituents of this index totaled 641 companies. The FTSE All-Share is the aggregation of the FTSE 100 Index and the FTSE 250 Index, which are together known as the FTSE 350 Index, and the FTSE SmallCap Index. The index is maintained by FTSE Russell, a subsidiary of the London Stock Exchange Group. It aims to represent at least 98% of the full capital value of all UK companies that qualify as eligible for inclusion.

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 chips listed on the London Stock Exchange.