Chiang Saen (Thai: เชียงแสน, pronounced [t͡ɕʰīa̯ŋ sɛ̌ːn]) is a district (amphoe) in the northern part of Chiang Rai province, northern Thailand. Chiang Saen is an important entrepôt for Thailand's trade with other countries on the upper part of Mekong River.