Potassium benzoate, the potassium salt of benzoic acid, is a food preservative that inhibits the growth of mold, yeast and some bacteria. It works best in low-pH products, below 4.5, where it exists as benzoic acid.

The mechanism starts with the absorption of benzoic acid in to the cell. If the intra cellular pKa changes to 5 or lower the anaerobic fermentation of glucose through phosphofructokinase is decreased by 95%. The effective of benzoic acid and benzoate is depending on the pKa of the food.

Acidic food and beverage like fruit juice (citric acid), sparkling drinks (carbon dioxide), soft drinks (phosphoric acid), pickles (vinegar) or other acidified food are preserved with potassium benzoate.

It is approved for use in most countries including Canada, the US, and the EU. In the EU, it is not recommended for consumption by children.

Cats have a significantly lower tolerance against benzoic acid and its salts than rats and mice.

This compound was humorously referred to in an episode of The Simpsons as an ingredient of toppings for frozen yogurt, otherwise known as "frogurt".