Fritessaus or frietsaus ("fries sauce") is a Dutch accompaniment to French fries, served popularly nationwide. It is similar to mayonnaise, but with at most 25% fat, is leaner and usually sweeter than mayonnaise. Mayonnaise in the Netherlands is required by the Warenwet (Commodities Act) of 1998 to contain at least 70% fat and at least 5% egg yolk before it may be called mayonnaise.

Although it is usually bought pre-made, frietsaus can be produced at home in a process similar to that which is used to make mayonnaise. It is usually thinned with water or other suitable liquids.^{[citation needed]}