Tanintharyi Region (Burmese: တနင်္သာရီတိုင်းဒေသကြီး, pronounced: [tənɪ́ɴθàjì táɪɴ dèθa̰ dʑí]; Mon: ဏၚ်ကသဳ or တနၚ်သြဳ; formerly Tenasserim Division and subsequently Tanintharyi Division, is an administrative region of Myanmar, covering the long narrow southern part of the country on the Kra Isthmus. It borders the Andaman Sea to the west and the Tenasserim Hills, beyond which lies Thailand, to the east. To the north is the Mon State. There are many islands off the coast, the large Mergui Archipelago in the southern and central coastal areas and the smaller Moscos Islands off the northern shores. The capital of the division is Dawei (Tavoy). Other important cities are Myeik (Mergui) and Kawthaung. The division covers an area of 43,344.9 km², and had a population of 1,406,434 at the 2014 Census.

In Thai, the region is known as "Tanao Si" (Thai: ตะนาวศรี, pronounced [tənaːw sǐː]), while in Malay, it is known as Malay: Tanah Sari (تانه ساري). "Tanah Sari Region" was part of "Tanah Melayu". Initially, it was occupied by Ayutthaya. Later, Burma occupied the region from Ayutthaya.

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