Wén Dān (Chinese: 文單; Thai: เหวินตัน) was a group of ancient Mon political entities that existed around the 7th–8th centuries CE in the interior of mainland Southeast Asia scattered around the central Mekong Valley in the present-day northeast Thailand.

[1][2][3] It was mentioned in the Chinese annals of the Tang period (618-907 AD) as a dependency on the trans-Mekong trade route from the ancient city of Chiaochih (jiāo zhǐ 交趾; Giao chỉ; near the present-day Vinh of Vietnam) to India.

[4]: 87–88  Jayavarman II probably either defeated Wen Dan and then moved the capital from Indrapura to Yaśodharapura in the north,[4]: 87  or formed ally with the communities in Mun and Chi watersheds to against Si Thep in the west.

Vietnamese Governor "He Lu Guang" joined Wen Tan in attacking the south, but Ko-lo-Feng, the Nanzhao king, captured General Li and won.

In 771, the prince of Wen Dan went to China and was titled "Special Highest Local Commander," equal to the King of Nanzhao, and was even higher than the Chinese governors in Vietnam and Guangzhou.