A mirepoix ( meer-PWAH; French: [miʁ.pwa]) is a mixture of diced vegetables cooked with fat (usually butter) for a long time on low heat without coloring or browning. The ingredients are not sautéed or otherwise hard-cooked, because the intention is to sweeten rather than caramelize them. Mirepoix is a long-standing part of French cuisine and is the flavor base for a wide variety of dishes, including stocks, soups, stews, and sauces.

When the mirepoix is not precooked, the constituent vegetables may be cut to a larger size, depending on the overall cooking time for the dish. Usually the vegetable mixture is onions, carrots, and celery (either common 'pascal' celery or celeriac), with the traditional ratio being 2:1:1—two parts onion, one part carrot, and one part celery. Further cooking, with the addition of tomato purée, creates a darkened brown mixture called pinçage.

Similar flavor bases include the Italian soffritto, the Spanish and Portuguese sofrito/refogado (braised onions, garlic and tomato), a variation with tomato paste instead of fresh tomato of the Eastern Mediterranean and Balkans region, the German Suppengrün (leeks, carrots and celeriac), the Polish włoszczyzna (leeks, carrots, celeriac and parsley root), the Russian/Ukrainian smazhennya or zazharka (onion, carrot and possibly celery, beets or pepper), the United States Cajun/Creole holy trinity (onions, celery and bell peppers), and possibly the French duxelles (mushrooms and often onion or shallot and herbs, reduced to a paste).