AC agar (All Culture Agar) is a microbiological culture medium for general use. This non-selective medium is used to cultivate a wide range of micro-organisms (aerobic, anaerobic and micro-aerophilic bacteria). Many aerobic pathogens and saprophytes can also be isolated and cultured using AC medium. This is an empirical medium (no precise composition is known) but it still contains the following ingredients: peptone, beef extract, yeast extract, malt extract, dextrose, ascorbic acid and agar. Peptone, yeast extract and malt extract serve as sources of carbon and nitrogen in addition to being a source of vitamins and co-factors. Dextrose serves as an energy source in the form of fermentable carbohydrates. Ascorbic acid present in the medium helps to improve the clarity of the medium.

Although this medium can be used for a large number of microorganisms, there is no universal culture medium and some bacteria cannot grow on conventional peptone agar media. This medium can also be used for sterility testing of solutions and biological products that do not contain mercury preservatives.