Kanchanaburi is the largest of the western provinces (changwat) of Thailand. The neighboring provinces are Tak, Uthai Thani, Suphan Buri, Nakhon Pathom, and Ratchaburi. In the west it borders Kayin State, Mon State, and the Tanintharyi Region of Myanmar.

The provinces of Thailand are administrative divisions of the government of Thailand. The country is divided into 76 provinces proper, with one additional special administrative area. They are the primary local government units and act as juristic persons. They are divided into amphoe (districts) which are further divided into tambon, the next lower level of local government.