Som tam (Thai/Isan ส้มตำ) is a spicy papaya salad originating in Laos and the Isan region of Thailand. Som (ส้ม) in Isan and Lao is sour, and tam (ตำ) means pounded. It is also sometimes written as som tum, som dtam or som dtum. Other names for the dish are papaya pok pok (from the sound produced when preparing the dish in a mortar), tam som or, in Lao and Isan, tam mak hung (ตำหมากหุ่ง) (mak hung is the Lao and Isan word for papaya).

The main ingredient is grated, unripe papaya, seasoned and pounded to a softened state in a mortar. Chilli, garlic, lime and fish sauce are also usually added, while beans and tomato are optional. There are many variations of the dish, some made with carrot instead of papaya. The dish combines the four main tastes of Thai cuisine: sweet papaya, sour lime, hot chilli and salty fish sauce. It is served at room temperature, traditionally with sticky rice.

In Laos and Isan the dish is normally more spicy and sour, while the Central Thai version is milder. Som tam Lao usually features fermented crab, while som tam Thai is prepared with dried shrimp.

Som tam can also be prepared with other unripe fruits, notably mango, in which case it is known as tam ma-muang.