Samlar machu (Khmer: សម្លម្ជូរ) is the Khmer language term for a category of sour (machu) soups (samlar, also samlor, salaw, or salor) popularly known in English as simply "Cambodian sour soup".
The sour flavour of the soup comes from the use of tamarind (Khmer: អម្ពិល) and certain tangy vegetables such as tomato (Khmer: ប៉េងប៉ោះ) and pineapple (Khmer: ម្នាស់), as well as Tiliacora triandra leaves (Khmer: ស្លឹកវល្លិយាវ). There are many types of Khmer sour soups, but the most popular variation is samlor machu moun (Khmer: សម្លម្ជូរមាន់) (sour chicken soup), which is notable for the use of pickled lime. Meat in this type of soup is usually that of either chicken, fish, or pork. In recent times, instead of using fresh tamarind, a powdered tamarind soup base is used. One popular brand is manufactured by Knorr.