The azuki bean (also spelled adzuki) is an annual vine widely grown throughout eastern Asia and the Himalaya for its small (approximately 5 mm) bean. The cultivars most familiar in northeast Asia have a uniform red color, but white, black, gray and variously mottled varieties are also known. Azuki beans are considerably lower in fat and digest easier than many other beans.

Genetic evidence indicates that the azuki bean was first domesticated in the Himalaya. It was cultivated in China and Korea before 1000 BC. It was later taken to Japan, where it is now the second most popular legume after the soybean.

The name azuki is a transliteration of the native Japanese name. Japanese also has a Chinese loanword, shôzu, which means "small bean" (its counterpart "large bean"  being the soybean). It is common to write shôzu in kanji but pronounce it as azuki.

In China, the corresponding name  is still used in botanical or agricultural parlance. However in everyday Chinese, the more common word is hongdou, meaning "red bean", because almost all Chinese cultivars are uniformly red. In English-language discussions of Chinese topics, the term "red bean" is often used (especially in reference to red bean paste), but in other contexts this usage can cause confusion with other beans that are also red.

Uses
In Chinese cuisine, Korean cuisine and Japanese cuisine, the azuki bean is almost always eaten sweetened. In particular, it is often boiled with sugar, resulting in red bean paste, a very common ingredient in all three cuisines.

Red bean paste is used in many Chinese foods, such as: tangyuan, zongzi, mooncakes, baozi. It is also used as a filling for Japanese sweets such as anmitsu, taiyaki, and daifuku. A more liquid version, using azuki beans boiled with sugar, lotus seeds and orange peel, produces a sweet dish called red bean soup. Azuki beans are also commonly eaten sprouted, or boiled in a hot, tea-like drink.