Greeley County is a county located in western Kansas, in the Central United States. Its county seat and largest city is Tribune. As of the 2020 census, the population was 1,284, making it the least populous county in Kansas. As of 2018, it is tied with Wallace County as the least densely populated county in the state. The county is named after Horace Greeley, editor of the New York Tribune, who encouraged western settlement with the motto "Go West, young man".

In 1854, the Kansas Territory was organized, and Kansas became the 34th U.S. state in 1861. In 1873, Greeley County was established. It was the last county in the state to be organized, which finally occurred in July 1888 after a lawsuit to stop organization on the basis of insufficient population was dismissed. Tribune was named the temporary county seat, defeating Horace in an election held that November.

Settlement in Greeley County was sparse until 1885, when the influx of settlers led to numerous town claims, with Horace, Tribune, and Reid among the settlements that boasted banks, newspapers, and basic amenities. The Missouri Pacific Railroad's arrival in 1887, with a depot at Tribune, facilitated further development. By 1910, the population had significantly increased, leading to the establishment of 13 school districts and a scattering of post offices including at Tribune, Horace, Hurt, Sidney, Thelma, and Youngville.

According to the United States Census Bureau, the county has a total area of 778 square miles (2,020 km²), all of which is land. It is the largest of five United States counties and twelve (Virginia) independent cities that officially have no water area.^{[citation needed]}

The county's landscape is predominantly prairie, with an elevation between 3,000 and 4,000 feet. White Woman Creek, the county's most notable watercourse, often runs dry.

As of the census of 2000, there were 1,534 people, 602 households, and 414 families residing in the county. The population density was 2 people per square mile (0.77 people/km²). There were 712 housing units at an average density of 1 per square mile (0.39/km²). The racial makeup of the county was 93.09% White, 0.26% Native American, 0.20% Black or African American, 0.13% Pacific Islander, 0.07% Asian, 5.22% from other races, and 1.04% from two or more races. Hispanic or Latino of any race were 11.54% of the population.

There were 602 households, out of which 34.20% had children under the age of 18 living with them, 61.10% were married couples living together, 4.50% had a female householder with no husband present, and 31.20% were non-families. 28.60% of all households were made up of individuals, and 12.80% had someone living alone who was 65 years of age or older. The average household size was 2.50 and the average family size was 3.10.

In the county, the population was spread out, with 28.20% under the age of 18, 6.80% from 18 to 24, 27.30% from 25 to 44, 19.90% from 45 to 64, and 17.70% who were 65 years of age or older. The median age was 39 years. For every 100 females there were 98.40 males. For every 100 females age 18 and over, there were 92.80 males.