Doenjang-guk (Korean: 된장국; pronounced [twen.dʑaŋ.k͈uk̚]) or soybean paste soup is a guk (soup) made with doenjang (soybean paste) and other ingredients, such as vegetables, meat, and seafood. It is thinner, lighter, and milder than doenjang-jjigae (soybean paste stew). It is similar to the Japanese miso soup.^{[citation needed]} It is sometimes mild, sometimes strong, and accompanied with rice most of the time.

Doenjang-guk is an example of a banchan, one of several small dishes served with meals at restaurants and in home cooking. Other banchan include kimchi, marinated vegetables, and pickled/salted seafood. This soup is perhaps the cheapest meal in Korea.

In the Joseon period, the royals had five meals (called sura), and in three of those they had doenjang-guk as a side dish (banchan; 반찬), specifically on a small table on the right side of the main table, together with other Korean traditional foods such as vegetables (chaeso; 채소), meat (kogi; 고기), egg, and sesame oil (chamgireum; 참기름).

The most simple form of this soup is clear soybean paste soup (malgeun-doenjangguk 맑은 된장국). It is mainly composed of a good fermented soybean paste and stock. It accompanies more complex one-bowl rice dishes that have many ingredients, like bibimbap with sliced raw fish and avocado, mushroom, and other vegetables. The ingredients for this soup are anchovy-kelp stock, vegetable stock, or unsalted chicken broth; doenjang paste; and optionally some scallions.

The most commonly eaten form of this dish is soybean paste soup with cabbage (baechu-doenjangguk; 배추된장국) and it is eaten at any time of the day. The broth has a deep, comforting flavor, the cabbage adds texture and sweetness, and it is light since there is no grease. The ingredients are dried anchovies; napa cabbage leaves, white-stemmed chard, or bok choy; doenjang; garlic; chili peppers; all-purpose flour or rice water; and fish sauce.

To make the broth for a doenjang-based soup or stew, it is common to begin with the water used to wash rice, ssaltteumul (쌀뜨물). This rice water adds starch to the soup and works as a binding agent between the soybean paste and the broth, while improving the flavor of the doenjang. A substitute can be made by mixing in a teaspoon of flour or rice flour.