Udon (うどん or 饂飩) is a thick noodle made from wheat flour, used in Japanese cuisine. There is a variety of ways it is prepared and served. Its simplest form is in a soup as kake udon with a mild broth called kakejiru made from dashi, soy sauce, and mirin. It is usually topped with thinly chopped scallions. Other common toppings include prawn tempura, kakiage (mixed tempura fritter), abura-age (sweet, deep-fried tofu pouches), kamaboko (sliced fish cake), and shichimi spice added to taste.

Standard broth differs by region. Dark (koikuchi) soy sauce is added in eastern Japan, while light (usukuchi) soy sauce is added in the west. Instant noodles are often sold in two (or more) versions accordingly.

More unusual variants include stir-fried yaki udon and curry udon made with Japanese curry. It is often used in shabu shabu or Japanese hot pot.