Nakhon Nayok Province covers 2,122 sq km (819 sq mi) and has a population of 254,000 people (2012 estimate). It ranks 66th in terms of size and 70th in terms of population, and 41st in terms of population density. The province is bordered by the Sankamphaeng Range to the north, where the highest point is the 1292-meter Yod Khao Kiew. The area is part of Khao Yai National Park. The Nakhon Nayok River is the main river flowing through the province.
Nakhon Nayok Province traces its history to the Dvaravati Kingdom which was established in the 11th century. Ruins from that period is still visible today in Mueang Boran Dong Lakhon, to the south of Nakhon Nayok Town. Nakhon Nayok was given its present name in 1350, when it came under the rule of the Kingdom of Ayutthaya. In 1943, the province was absorbed by Prachinburi Province, but was again separated out in 1946.
Nakhon Nayok Province comprises 4 districts or amphoe, namely Mueang Nakhon Nayok, Pak Phli, Ban Na and Ongkharak. These are subdivided into 41 subdistricts or tambon and 403 villages or muban.