Som tum (also spelled som tam) is a Thai salad of shredded green (unripe) papaya, tossed and lightly pounded with tomatoes, chilies, lime juice, fish sauce, and crushed peanuts. It originated in Thailand's northeastern Isan region and is regarded as a national dish.
The name means roughly "sour pounded [thing]," referring to both the salad's tartness and the pounding used to bruise and mix the ingredients in a mortar and pestle. The dish spans a spectrum of regional versions: the Isan/Lao original (som tam Lao or som tam pla ra) uses fermented fish sauce (pla ra) and no peanuts, giving it a funkier, more sour and savory profile, while the milder, sweeter "som tam Thai," with dried shrimp and peanuts, is a Bangkok adaptation that spread nationally as Isan migrants brought the dish to the capital. A southern variant, som tam boo, adds salted crab.
Som tum is usually eaten with sticky rice and grilled meats, and is central to Isan identity, served at family meals, festivals, and celebrations.