| Jurisdiction: | Diocese |
| Border: | Catholic |
| Tandag | |
| Latin: | Dioecesis Tandagensis |
| Local: | Diyosesis sa Tandag Diyosesis ng Tandag |
| Coat: | Diocese of Tandag Coat of arms.svg |
| Coat Size: | 150px |
| Country: | Philippines |
| Territory: | Surigao del Sur |
| Province: | Cagayan de Oro |
| Metropolitan: | Cagayan de Oro |
| Deaneries: | 4 |
| Coordinates: | 9.0445°N 126.2125°W |
| Area Km2: | 4,862 |
| Population: | 752,496 |
| Population As Of: | 2021 |
| Catholics: | 592,968[1] |
| Catholics Percent: | 78.8 |
| Denomination: | Roman Catholic |
| Established: | 16 June 1978 |
| Cathedral: | New Cathedral of Saint Nicholas of Tolentino in Tandag |
| Patron: | Saint Nicholas of Tolentino San Nicolas de Tolentino |
| Bishop: | Raul Dael |
| Metro Archbishop: | José A. Cabantan |
| Suffragan: | for one --> |
| Vicar General: | Isidro H. Irizari, PC, VG |
| Episcopal Vicar: | Arturo P. Langit Jaime B. Panares |
| Archdeacon: | for one--> |
The Roman Catholic Diocese of Tandag (Lat: Dioecesis Tandagensis) is a diocese of the Latin Church of the Roman Catholic Church in the Philippines.
Erected in 1978, the diocese was created from territory in the Diocese of Surigao.
The diocese has experienced no jurisdictional changes, and is a suffragan of the Archdiocese of Cagayan de Oro.
On 26 February 2018, Pope Francis named Raul B. Dael, Vicar for the Clergy of the Archdiocese of Cagayan de Oro as the bishop of Tandag replacing Nereo P. Odchimar after Odchimar reaching the mandatory age of retirement, which was accepted by Pope Francis.[2]
On top, on a blue / azure field symbolizing fidelity and truth, the crucifix with intertwined lily, a loaf of bread on a plate, and the star—all depicted proper—attributes of St. Nicholas of Tolentino, principal patron of the Diocese. To the left of the attributes, the blessing hand with brown glove, depicted proper, an allusion to Padre San Pio of Pietrelcina, secondary patron of the Diocese.On base, on a green / vert field symbolizing hope and lush vegetation, the heraldic symbol for mountains in gold / or, symbolizing the rich resources of the Province of Surigao del Sur. The symbol alludes to the Diwata mountain range located in the Province. Beneath is the heraldic symbol for water in blue / azure, symbolizing the Philippine Sea, the body of water bordering the coastline of the Province.
| 1. | Ireneo A. Amantillo, C.SS.R. | 6 Sep 1978 Appointed - 18 Oct 2001 Resigned | |
| 2. | Nereo P. Odchimar | 18 Oct 2001 Appointed - 26 Feb 2018 Retired | |
| 3. | Raul B. Dael | 26 Feb 2018 Appointed | |