Rujak (Indonesian spelling) or rojak (Malay spelling) is a salad dish of Javanese origin, commonly found in Indonesia, Malaysia, and Singapore. The most popular variant in all three countries is composed of a mixture of sliced fruit and vegetables and served with a spicy palm sugar dressing.

There is a variety of preparations, especially in Indonesian cuisine, and rujak is widely available throughout the country. The most common variant is primarily composed of fruits and vegetables, and its sweet and tangy dressing is often made with shrimp paste. Some recipes may contain seafood or meat components, especially in Malaysia and Singapore, where a notable variant shows influence from Indian Muslim cuisine.

According to the Dutch missionary Petrus Josephus Zoetmulder, the word "rujak" comes from the Old Javanese word anrujak or rinujak, which means "to chop into little pieces". Alternatively, its origin may be the word rurujak, meaning a mixture of chopped unripe fruit, as attested in the ancient Taji Inscriptions (901 CE) from the era of the Mataram Kingdom in Central Java.

The dish was later introduced to other regions and neighboring countries by the Javanese diaspora as well as by Indian migrants from Java. In Malaysia and Singapore, it is spelled "rojak".

In Indonesia, particularly among the Javanese, the sweet, spicy, and sour tastes of rujak are popular among pregnant women; this craving for unripe mango and other sour-tasting fruits is known as ngidham or nyidham in Javanese. In Javanese culture, rujak is an essential part of the traditional prenatal ceremony called naloni mitoni or tujuh bulanan (literally: "seventh month") and is meant to wish the mother-to-be a safe, smooth, and successful labour. The recipe for this ceremony is similar to typical fruit rujak, with the exceptions that the fruits are roughly shredded instead of thinly sliced, and that jeruk bali (pomelo/pink grapefruit) is an essential ingredient. Javanese people believe that if the rujak tastes sweet, the child will be a girl, and if it is spicy, it will be a boy.

Mangarabar, or rujak-making, is a special event for the Batak and Mandailing people of Tapanuli, North Sumatra, following a harvest, with entire villages getting involved.

In Malaysia and Singapore, "rojak" is also used as a colloquial expression for an eclectic mix, in particular as a word describing the multiethnic character of the two societies.

In Indonesia, rujak buah is also known as rujak manis (sweet rujak). The typical Indonesian fruit rujak consists of slices of assorted tropical fruits, such as water apple, pineapple, unripe mango, jícama, cucumber, kedondong, and sweet potato. Sometimes, variants of green apple, bilimbi, and pomelo are added. The sweet and spicy rujak dressing is made of water, palm sugar, tamarind, crushed peanuts, shrimp paste (known locally as petis), salt, and bird's eye chili.