Tartar sauce or tartare sauce is a thick white sauce made from mayonnaise and finely chopped pickled cucumber, capers, onions (or chives), and fresh parsley. Chopped hard-boiled eggs, olives, and horseradish are sometimes added, and dijon mustard is often used as an emulsifier. It is frequently used to season fried seafood dishes. It can also be made by mixing commercially produced relish and mayonnaise. Vinegar can be added for a sharper flavor. The sauce is typically of a rough consistency.
Other typical variants contain Worcestershire sauce, red pepper sauce, lemon juice, or black pepper.
The name derives from the Tatars, a Turkic people who live primarily in Russia. The sauce was not, however, invented or ever even used by the Tatars but the French, who served it as a condiment for steak tartare. Tartar sauce is very commonly spelled "tartare" in many European countries as well as Australia and New Zealand. This is based on the original French phrase sauce tartare.