In Belgium, what creamy sauce is a traditional dip for fries?

In Belgium, mayonnaise is a traditional creamy dip for fries.

Belgian friteries—specialist fry shops often called frietkots or frituurs—serve fries with a wide selection of sauces, but mayonnaise is the classic pairing. It is commonly spooned over fries served in a paper cone or carton.

Belgian fries are traditionally fried twice: the first frying cooks the potato, while the second creates a crisp exterior. Their sauce culture is broader than mayonnaise alone; tartar sauce, curry ketchup, and many mayonnaise-based sauces are also popular. This is why answers such as mustard or tzatziki can sound plausible but are not the canonical traditional answer to this question.

Mayonnaise is also the base of several Belgian specialties, including sauce andalouse and samurai sauce. Belgian fries are often eaten as a snack by themselves or alongside fried foods, stews, mussels, or a mitraillette sandwich.