Thong Lan (Thai: ทองลัน) was a king of Ayutthaya, an ancient kingdom in Thailand.

A son of Borommarachathirat I and member of the House of Suphannaphum, Thong Lan succeeded his father to the throne of Ayutthaya in 750 LE (1931 BE, 1388/89 CE) at the age of 15. Having reigned for only seven days, he was deposed and executed in a coup by Ramesuan, his relative from the House of Uthong.

Thong Lan was the first monarch of Ayutthaya to be executed.