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CAC (Cotation Assistée en Continu) is an electronic trading system implemented at the Paris Bourse, the French stock exchange, in the late 1980s. It was introduced in 1986 for the handling of less liquid equities, and in 1989 it was operational for all listed stocks. The acronym is also used to refer to the CAC 40 which is a stock index provided by the Paris Bourse. Curiously, the acronym does also fit the name of the early Parisian stockbrokers' association, the "Compagnie des Agents de Change". The CAC system is in fact a version of an earlier system that was developed by the Toronto Stock Exchange in the mid-1970s: CATS (Computer Assisted Trading System). In the early 1990s the Paris Bourse developed an upgraded technology known as NSC (Nouveau Système de Cotation), which served as a technological platform for the Euronext initiative.

CAC, like CATS, was an order-driven market platform that handled the process of order matching and price setting through a double auction algorithm. It allowed for a full automation of quotation in a centralised, order-driven exchange (which eventually may translate into the disappearance of the open outcry).