兰甘亨大帝（泰文：พ่อขุนรามคำแหงมหาราช ，约1239年－1298年） 泰国素可泰王朝第三代国王，中国史称敢木丁。

兰甘亨的父亲室利·膺沙罗铁是素可泰王朝创始人。其兄班孟是素可泰王朝的第二代国王，1278年去世后，兰甘亨继位。兰甘亨19岁时随父与功德城的君主沙木槎作战。室利·因陀罗的士兵战败而逃，只有兰甘亨一人驱赶战象，坚持战斗，结果转败为胜。因而他父亲给他命名为甘亨，即勇敢的意思。后人称他为坤兰甘亨，是因为坤是素可泰时期对国王的称呼，兰是梵文“伟大”之意，坤兰甘亨意即“勇敢而伟大的君主”。

King Ram Khamhaeng (Thai:พ่อขุนรามคำแหง; rtgs: Pho Khun Ram Khamhaeng; c. 1237/1247 – 1298) was the third king of the Phra Ruang dynasty, ruling the Sukhothai Kingdom (a forerunner of the modern kingdom of Thailand) from 1279–1298, during its most prosperous era. He is credited with the creation of the Thai alphabet and the firm establishment of Theravada Buddhism as the state religion of the kingdom. Recent scholarship has cast doubt on his role, however, noting that much of the information relating to his rule may have been fabricated in the 19th century in order to legitimize the Siamese state in the face of colonial threats.