| Jurisdiction: | Diocese |
| Nakhon Sawan | |
| Latin: | Dioecesis Nakhonsauanensis |
| Local: | Thai: สังฆมณฑลนครสวรรค์ |
| Country: |  Thailand |
| Province: | Bangkok |
| Metropolitan: | Bangkok |
| Area Km2: | 93,547 |
| Population: | 8.2 million |
| Population As Of: | 2006 |
| Catholics: | 9,237 |
| Catholics Percent: | 0.1 |
| Denomination: | Catholic |
| Sui Iuris Church: | Latin Church |
| Rite: | Roman Rite |
| Cathedral: | St Anne's Cathedral in Nakhon Sawan |
| Bishop: | Paul Tawat Singsa |
| Metro Archbishop: | Kriengsak Kovitvanit |
The (Roman Catholic) Diocese of Nakhon Sawan (Dioecesis Nakhonsauanensis, Thai: สังฆมณฑลนครสวรรค์) is located in central Thailand. It is a suffragan diocese of the archdiocese of Bangkok.
The diocese covers an area of 93,547 km2, covering 13 provinces - Chainat, Kamphaeng Phet, Lopburi, Nakhon Sawan, Saraburi, Sukhothai, Tak, Uthai Thani, Uttaradit.
As of 2001, of the 8.2 million citizen 9,237 are member of the Catholic Church. It is divided into 28 parishes, having 27 priests altogether.
The diocese was erected on February 9, 1967, when it was split off from the archdiocese of Bangkok.
The St. Anna Cathedral is located in downtown Nakhon Sawan (15.6936°N 100.1203°W).