Udon (うどん; rarely 饂飩 or 餛飩) is a type of thick wheat-based noodle popular in Japanese cuisine. Udon is said to have been imported to Japan from China in the 6th century. This original udon was 2 to 3cm in diameter, a flat pancake shaped "noodle" added to the miso-based soup, and in modern Chinese the characters 餛飩 refer to wonton dumplings, not noodles.
They are usually served in a mildly flavored broth (e.g., as Kake Udon served in Kake Jiru made of dashi, Japanese soy sauce (shoyu) and mirin), and they may be topped with tempura of shrimp or kakiage , or fried tofu pockets.
The flavor of broth and topping vary from region to region.
There are wide variations in both thickness and shape.
- Inaniwa (稲庭) udon
- Ise (伊勢) udon 
- Kansai (関西) udon
- Kishimen (きし麺)
- Kitsune (きつね) udon
- Sanuki (讃岐) udon
- Sōki soba (ソーキそば) - Despite its name, it is possible that this regional Okinawan dish may be classified as udon.
- Tanuki (たぬき) udon - What is known as "tanuki udon" varies from region to region.
- Tsuji, Shizuo. (1980). Japanese cooking: A simple Art. Kodansha International/USA, New York.