The Diocese of Gallup is a Latin Church ecclesiastical territory, or diocese, of the Catholic Church in northwestern New Mexico and northeastern Arizona in the United States. It is a suffragan diocese in the ecclesiastical province of the metropolitan Archdiocese of Santa Fe.

Gallup is a city in McKinley County, New Mexico, United States, with a population of 21,899 as of the 2020 census. A substantial percentage of its population is Native American, with residents from the Navajo, Hopi, and Zuni tribes. Gallup is the county seat of McKinley County and the most populous city between Flagstaff and Albuquerque, along historic U.S. Route 66.