Financial Times Stock Exchange Index . An index of the share prices of the largest companies (by market capitalisation) in the UK.  FTSE 100 is the index of the top 100 companies. FTSE All-Share is the index of all listed companies. There are other FTSE indices too. FTSE is a trademark jointly owned by the London Stock Exchange plc and The Financial Times Limited and is used by FTSE International Limited (“FTSE”) under licence. The FTSE 100 index is calculated solely by FTSE. FTSE does not sponsor, endorse, or promote this website and is not in any way connected to it and does not accept any liability in relation to its issue, operation and trading. All copyright in the index values and constituent list vests in FTSE.