CAC 40 (Cotation Assistée en Continu) is a French stock market index. Capitalization-weighted index of the top 40 equities among the top 100 highest market capitalizations traded on the Euronext Paris exchange in the previous month (formerly, the Paris Bourse). It measures price return. This is one of the primary national indexes of the pan-European stock market group Euronext, along with the BEL20 in Brussels, the PSI-20 in Lisbon, and the AEX in Amsterdam.

France's CAC 40 index is the benchmark stock market index for the Euronext Paris, representing the 40 largest and most actively traded French companies. “CAC” stands for Cotation Assistée en Continu (Continuous Assisted Quotation). It includes major firms like L'Oréal, TotalEnergies, Airbus, and LVMH, covering diverse sectors such as energy, luxury, banking, and technology. The index is capitalisation-weighted, meaning companies with larger market value have more influence on its performance. Often viewed as a key indicator of the French economy and broader European market trends, the CAC 40 is updated every 15 seconds during trading hours. Investors and analysts use it to track market performance, economic sentiment and to make informed trading or investment decisions.