The Plain of Jars (Lao: ທົ່ງໄຫຫີນ Thong Hai Hin, [tʰōŋ hǎj hǐn]) is a megalithic archaeological landscape in Laos. It consists of thousands of stone jars scattered around the upland valleys and the lower foothills of the central plain of the Xiangkhoang Plateau. The jars are arranged in clusters ranging in number from one to several hundred.

The Xiangkhoang Plateau is at the northern end of the Annamese Cordillera, the principal mountain range of Indochina. French researcher Madeleine Colani concluded in 1930 that the jars were associated with burial practices. Excavation by Lao and Japanese archaeologists in the intervening years has supported this interpretation with the discovery of human remains, burial goods and ceramics around the jars. Researchers (using optically stimulated luminescence) determined that the jars were put in place as early as 1240 to 660 BC. The jars at Site 1 (using detrital zircon geochronology) were determined to have been transported to their current location from a presumed quarry eight kilometers away. The Plain of Jars is one of the most important prehistoric sites in Southeast Asia.