Morrow County is one of the 36 counties in the U.S. state of Oregon. As of the 2020 census, the population was 12,186. The county seat is Heppner. The county is named for one of its first settlers, Jackson L. Morrow, who was a member of the state legislature when the county was created. Half of the Umatilla Chemical Depot, which includes the Umatilla Chemical Agent Disposal Facility, and the Naval Weapons Systems Training Facility Boardman are located within the county. Morrow County is part of the Pendleton-Hermiston, OR, Micropolitan Statistical Area. It is located on the south side of the Columbia River and is included in the eight-county definition of Eastern Oregon.

Heppner is a city in, and the county seat of, Morrow County, Oregon, United States. As of 2010, the population was 1,291. Heppner is part of the Pendleton-Hermiston Micropolitan Area. Heppner is named after Henry Heppner, a prominent Jewish-American businessman.