| Jurisdiction: | Diocese |
| Udon Thani | |
| Latin: | Dioecesis Udonthaniensis |
| Local: | Thai: สังฆมณฑลอุดรธานี |
| Country: |  Thailand |
| Metropolitan: | Archdiocese of Thare and Nonseng |
| Area Km2: | 50,046 |
| Population: | 5,371,000 |
| Population As Of: | 2010 |
| Catholics: | 16,822 |
| Catholics Percent: | 0.3 |
| Denomination: | Catholic |
| Sui Iuris Church: | Latin Church |
| Rite: | Roman Rite |
| Cathedral: | Cathedral of Our Mother of Perpetual Help |
| Bishop: | Joseph Luechai Thatwisai |
| Metro Archbishop: | Anthony Weradet Chaiseri |
| Map: | Thailand Diocese Udon Thani.png |
The (Roman Catholic) Diocese of Udon Thani (Dioecesis Udonthaniensis, Thai: สังฆมณฑลอุดรธานี) is in northeast Thailand. It is a suffragan diocese of the archdiocese of Thare and Nonseng.
The diocese covers an area of 50,046 km², covering five provinces of Thailand: Khon Kaen, Loei, Nongbua Lamphu, Nong Khai, and Udon Thani. As of 2001, of the 5.3 million citizens, 5,612 are members of the Catholic Church. It is divided into 56 parishes, having 31 priests altogether.
The Prefecture Apostolic of Udonthani was created on May 7, 1953, when the Vicariate Apostolic of Thare was split. On December 18, 1965 the Prefecture Apostolic was elevated to a diocese.
The Cathedral of Our Mother of Perpetual Help (Thai: อาสนวิหารพระมารดานิจจานุเคราะห์) is located in Udon Thani town.