Deuel County (/ˈduːəl/) is a county located in the U.S. State of Nebraska. As of the 2020 United States census, the population was 1,838. Its county seat is Chappell. The county was formed in 1889 and named for Harry Porter Deuel, superintendent of the Union Pacific Railroad.

In the Nebraska license plate system, Deuel County is represented by the prefix 78 (it had the 78th-largest number of vehicles registered in the county when the license plate system was established in 1922).

Deuel County lies on the south side of Nebraska. Its southern boundary abuts the northern boundary line of the State of Colorado. According to the US Census Bureau, the county has an area of 411 square miles (1,060 km²), of which 440 square miles (1,100 km²) is land and 0.9 square miles (2.3 km²) (0.2%) is water.

Since Deuel County lies in the western portion of Nebraska, its residents observe Mountain Time. The eastern portion of Nebraska observes Central Time.

As of the 2020 census, the county had a population of 1,838. The median age was 49.9 years. 21.4% of residents were under the age of 18 and 25.6% of residents were 65 years of age or older. For every 100 females there were 102.6 males, and for every 100 females age 18 and over there were 106.6 males age 18 and over.

The racial makeup of the county was 93.0% White, 0.1% Black or African American, 0.7% American Indian and Alaska Native, 0.3% Asian, 0.0% Native Hawaiian and Pacific Islander, 1.8% from some other race, and 4.1% from two or more races. Hispanic or Latino residents of any race comprised 5.4% of the population.

0.0% of residents lived in urban areas, while 100.0% lived in rural areas.

There were 834 households in the county, of which 26.0% had children under the age of 18 living with them and 20.5% had a female householder with no spouse or partner present. About 33.6% of all households were made up of individuals and 17.0% had someone living alone who was 65 years of age or older.