Umatilla County () is one of the 36 counties in the U.S. state of Oregon. Its 2020 population of 80,075 ranks it as the 14th largest in Oregon, and largest in Eastern Oregon. Hermiston is the largest and fastest growing city in Umatilla County, but Pendleton remains the county seat. Umatilla County is part of the Hermiston-Pendleton, OR Micropolitan Statistical Area, which has a combined population of 94,833.
Geography
alt=Map of Umatilla County|thumb|Map of Umatilla County
According to the United States Census Bureau, the county has a total area of , of which are land and (0.5%) are covered by water. It borders the Columbia River across from Washington.
Adjacent counties
thumb|250px|[[Interstate 84 in Oregon|I-84 eastbound and McKay Reservoir in Umatilla County]]
- Benton County, Washington (north)
- Walla Walla County, Washington (north)
- Columbia County, Washington (northeast)
- Wallowa County (east)
- Union County (east)
- Grant County (south)
- Morrow County (west)
National protected areas
- Cold Springs National Wildlife Refuge
- McKay Creek National Wildlife Refuge
- Umatilla National Forest (part)
- Whitman National Forest (part)