Malheur County is a county located in the southeast corner of the U.S. state of Oregon. As of the 2010 census, the population was 31,313. Its county seat is Vale, and its largest city is Ontario. The county was named after the Malheur River, which runs through the county. "Malheur" is French for misfortune or tragedy.
Malheur County is included in the Ontario, OR-ID Micropolitan Statistical Area, which is also included in the Boise City-Mountain Home-Ontario, ID-OR Combined Statistical Area. It is included in the eight-county definition of Eastern Oregon. The county shares a border with Baker County to the north, the state of Idaho to the east, the state of Nevada to the south, Harney County to the west, and Grant County to the northwest.