The town is built on a hill slope on the site of an ancient city which, for hundreds of years, served as the principal port of Siam.

These variations include Tanaosi or Tannaw (Siamese); Tanah Sari (Malay); Tenanthari, Tanncthaice, Ta-nen-tkd-ri, and Tanang-sci (Burmese); and Ta-na-ssu-li-sen (Chinese).

[7] Other sources have referred to it as Thenasserim, Tenáscri, Tciiaçar, Tanater, Tarnassari, Tenazar, Tannzzari, Tanaçari, Tanaçary, Tanaçarim, Taunararin, Tanaçarij, Tcnaiarij, Tanacarim, Tanassarim, Tenassarim, Tenasari, Tanussarin, Tenascri, Dahnnsari, Tanaseri, Tenauri, Tanasserin, Tananarino, Tenassarim, Tenassere, Tanararij, Tanassaria, Tonazarin, and Denouservn.

[8] The town's importance as a trade centre depended on it serving as the starting-point on the western coast of Siam as an overland route to the capital, Ayutthaya, which controlled the region during the 15th to 18th centuries.

Settlements close to Tanintharyi include Kadaw to the west, Mawtone across the river to the north-west and Bangyok to the north-east.

[1] It is characterized by a narrow coastal zone flanked by mountains, and is situated between the Gulf of Martaban and Victoria Point, just north of the Equator.