Nakhon Si Thammarat is a city municipality located in Mueang Nakhon Si Thammarat, which serves as the capital of Nakhon Si Thammarat Province in southern Thailand. The province is situated on the east coast of the Malay Peninsula, approximately 610 km (380 mi) south of Bangkok.
Historically, the city served as the administrative center of Southern Thailand for much of its history. While it was originally a coastal city, silting processes eventually moved the coastline away from the urban area. The city's geography is characterized by a north-to-south extension that is significantly larger than its west-to-east width, a layout dating back to its original location on a flood-safe dune.
The modern city center is located at the train station, situated to the north of the Old Town. As of 2019, the population of Nakhon Si Thammarat was recorded at 102,152 residents.