The Japanese term for a ramen soup base made from pork bones is tonkotsu.
The word literally means “pork bone” in Japanese: ton means pork and kotsu means bone. Tonkotsu broth is made by simmering pork bones, often for many hours, until collagen, marrow, and fat create a rich, opaque, creamy-looking soup. Onion, garlic, ginger, scallions, pork fat, trotters, or chicken bones may also be added, depending on the recipe.
Tonkotsu ramen is especially associated with Kyushu, Japan, particularly Fukuoka Prefecture. The style is commonly linked to Kurume, where it was developed in the 1930s, before spreading to Hakata and becoming internationally famous. Hakata-style bowls often feature thin, straight noodles, sliced chashu pork, green onions, and pickled ginger.
A common mix-up is confusing tonkotsu with the ramen’s seasoning base. Shoyu means soy sauce, shio means salt, and miso means fermented soybean paste; these describe flavor profiles. Tonkotsu specifically identifies the pork-bone broth, which can sometimes be combined with shoyu or miso.